JP2006039510A - Semiconductor display device and driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor display device with less generation of a pseudo contour while the drive frequency of a driver circuit is suppressed and to provide a semiconductor display device with less generation of a pseudo contour while the decrease in image quality is suppressed. <P>SOLUTION: The semiconductor display device comprises a table storing data for determining a relationship between the gray scale level of a video signal and a subframe period for light emission in a plurality of subframe periods, a controller for converting a video signal in accordance with the data and outputting the converted signal, and a panel whose pixel gray scale level is controlled in accordance with the outputted video signal. The number and the length of the plurality of subframe periods for each gray scale level of 2 or more are determined in accordance with a subframe ratio R<SB>SF</SB>which is calculated in accordance with a sharing ratio R<SB>sh</SB>determined by the frame frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor display device that performs display by a time gray scale method and a driving method of the semiconductor display device.

  A binary voltage included in a digital video signal is used for a driving method of a light-emitting device which is one of semiconductor display devices, and a gradation is controlled by controlling a time during which a light-emitting element of a pixel emits light during one frame period. There is a time gray scale method to display. In general, it can be said that the time gray scale method is more suitable because the electroluminescent material has a higher response speed than liquid crystal. Specifically, when displaying by the time gray scale method, one frame period is divided into a plurality of subframe periods. Then, in accordance with the video signal, the light emitting element of the pixel is turned on or off in each subframe period. With the above structure, the total length of the period during which the light emitting element of the pixel actually emits light during one frame period can be controlled by the video signal, so that gradation can be displayed.

  However, when displaying by the time gray scale method, there is a problem that a pseudo contour is displayed in the pixel portion depending on the frame frequency. Pseudo contour is an unnatural contour line that is often seen when intermediate gray levels are displayed by the time gray scale method, and is mainly caused by fluctuations in perceived luminance caused by human visual characteristics. .

  The pseudo contour includes a moving image pseudo contour generated when a moving image is displayed and a still image pseudo contour generated when a still image is displayed. In a pseudo-contour, a subframe period included in a previous frame period and a subframe period included in a subsequent frame period are visually recognized by human eyes as a continuous frame period. It happens by being done. In other words, the moving image pseudo contour is an unnatural bright line or dark line that is displayed on the pixel portion when a gradation different from the gradation that should be displayed in the original frame period is recognized by the human eye. Equivalent to. The generation mechanism of the still image pseudo contour is the same as that of the moving image pseudo contour. When displaying still images, a still image pseudo-contour shows a moving image as if pixels are near the boundary because the human viewpoint slightly moves left and right and up and down at the boundary between regions with different gradations. It occurs by seemingly. In other words, the still image pseudo contour corresponds to an unnatural bright line or dark line that is generated so as to oscillate near the boundary when a moving image pseudo contour is generated in a pixel near the boundary between regions having different gradations.

As a technique for preventing the above-described pseudo contour, Patent Document 1 below describes a plasma display driving method in which a subframe period in a light emission state appears continuously within one frame period. By the above driving method, a situation in which the period in which light is emitted and the period in which light is not emitted within one frame period does not reverse each other between adjacent frame periods can be prevented, so that pseudo contour can be suppressed. It is said that.
JP 2000-231362 A (paragraph 0023)

  However, in the driving method described in Patent Document 1, the total number of gradations matches the number of subframe periods that appear within one frame period. Therefore, if the number of subframe periods is increased in order to increase the total number of gradations, it is necessary to shorten each subframe period. However, normally, a video signal must be input to all rows of pixels every subframe period. Therefore, when the subframe period is too short, it is necessary to increase the drive frequency of the drive circuit. Therefore, considering the reliability of the drive circuit, it is not preferable to shorten the subframe period unnecessarily.

  Note that each subframe period can be lengthened to some extent by lengthening the frame period. However, even if the frame period is lengthened, it is not possible to expect a dramatic increase in the total number of gradations, and it is not preferable because pseudo contours are more likely to occur.

  Therefore, Patent Document 1 also describes a technique for performing pseudo image processing such as dithering and increasing the total number of gradations to be displayed in a pseudo manner without increasing the number of subframes. However, when image processing such as dithering is performed, a high total number of gradations can be displayed. However, since the image is displayed in a rough manner as if sanding is performed, deterioration in image quality is inevitable.

  In view of the above-described problems, an object of the present invention is to propose a method for driving a semiconductor display device that can suppress the generation of pseudo contours while suppressing the drive frequency of the drive circuit. Another object of the present invention is to propose a method for driving a semiconductor display device that can suppress the occurrence of a pseudo contour while suppressing a decrease in image quality.

  Another object of the present invention is to propose a semiconductor display device capable of suppressing the generation of pseudo contours while suppressing the driving frequency of the driving circuit. It is another object of the present invention to provide a semiconductor display device that can suppress the occurrence of pseudo contours while suppressing deterioration in image quality.

  The present inventor has found that the pseudo contour is less likely to occur as the ratio of the sub-frame period in the light emission state in common is larger in both frame periods before and after the gradation is changed by one step. . Therefore, in the present invention, the ratio of the lengths of the subframe periods that are in the light emission state (sharing ratio) in two frame periods having different gradations by one level is set to such an extent that the generation of pseudo contours can be suppressed. Increase and drive.

  Note that the sharing rate can be obtained by comparing a frame period of a specific gradation with a frame period of a gradation one step higher than the frame period.

  The lowest sharing rate that will be effective in suppressing the false contour can be determined by the frame frequency. Then, by using the obtained sharing ratio and the total number of gradations to be displayed, the length of each subframe period and the subframe period to be brought into a light emission state when displaying the gradation of each stage are obtained. Can be determined by calculation.

According to the driving method of the present invention, the subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency, and one frame period in each gray level of 2 or higher so as to satisfy the sub frame rate R _SF. The number and length of a plurality of subframe periods included in the subframe period and a subframe period in which light is emitted among the plurality of subframe periods are defined.

According to the light emitting device of the present invention, according to the subframe rate R _SF , the number and length of a plurality of subframe periods included in one frame period in each gradation of gradation 2 or higher, and the light emission state among the plurality of subframe periods A table in which data for determining a subframe period to be stored is stored, a number of bits included in the video signal according to the data and a controller that converts information included in each bit, and the video signal subjected to the conversion The sub-frame rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency.

  Note that in this specification, a light-emitting element includes an element whose luminance is controlled by current or voltage, specifically, an OLED (Organic Light Emitting Diode) or a FED (Field Emission Display). MIM type electron source elements (electron emitting elements) and the like are included.

  An OLED (Organic Light Emitting Diode), which is one of the light emitting elements, includes a layer (hereinafter referred to as an electroluminescent layer) containing an electroluminescent material from which luminescence generated by applying an electric field is obtained, an anode, And a cathode. The electroluminescent layer is provided between the anode and the cathode, and is composed of a single layer or a plurality of layers. In some cases, these layers contain an inorganic compound. Luminescence in the electroluminescent layer includes light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state.

  The semiconductor display device of the present invention includes a liquid crystal display device, a DMD (Digital Micromirror Device), and a PDP (Plasma Display Panel), in addition to a light emitting device that includes a light emitting element typified by an organic light emitting element (OLED) in each pixel. , FED (Field Emission Display), and other display devices capable of display by a time gray scale method are included in the category.

  The light-emitting device includes a panel in which the light-emitting element is sealed, and a module in which an IC including a controller or the like is mounted on the panel.

  Note that as a transistor used in the light-emitting device of the present invention, a polycrystalline semiconductor, a microcrystalline semiconductor (including a semi-amorphous semiconductor), or a thin film transistor using an amorphous semiconductor can be used. It is not limited to a thin film transistor. A transistor formed using single crystal silicon or a transistor using SOI may be used. Further, a transistor using an organic semiconductor or a transistor using carbon nanotubes may be used. In addition, the transistor provided in the pixel of the light-emitting device of the present invention may have a single gate structure, a double gate structure, or a multi-gate structure having more gates.

A semi-amorphous semiconductor is a film containing a semiconductor having an intermediate structure between amorphous and crystalline structures (including single crystal and polycrystal). This semi-amorphous semiconductor is a semiconductor having a third state which is stable in terms of free energy, and is a crystalline one having a short-range order and having a lattice strain, and having a grain size of 0.5 to 20 nm. It can be dispersed in a single crystal semiconductor. The semi-amorphous semiconductor has its Raman spectrum shifted to a lower wavenumber than 520 cm ⁻¹ , and diffraction peaks of (111) and (220) that are derived from the Si crystal lattice in X-ray diffraction are observed. . Further, in order to terminate dangling bonds (dangling bonds), hydrogen or halogen is contained at least 1 atomic% or more. Here, for convenience, such a semiconductor is referred to as a semi-amorphous semiconductor (SAS). Further, by adding a rare gas element such as helium, argon, krypton, or neon to further promote lattice distortion, stability is improved and a good semi-amorphous semiconductor can be obtained.

  With the above configuration, the present invention does not require the total number of gradations and the number of subframe periods to be the same as in the prior art, so that display can be performed with a higher total number of gradations while suppressing the number of subframes. . Therefore, the total number of gradations can be increased without performing processing such as dithering that lowers the image quality.

  Then, by performing driving so as to satisfy the sharing rate equal to or higher than the obtained value, it is possible to prevent the false contour while suppressing the frame frequency and the driving frequency of the driving circuit.

  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.

The present inventor conducted the following experiment in order to investigate the relationship between the sharing rate and the occurrence of the pseudo contour. First, one frame period is divided into _two subframe periods SF ₁ and SF ₂ , and a pattern as shown in FIG. 1 is displayed in the first frame period and the second frame period. Specifically, to display a checkerboard pattern in the sub-frame periods SF _1, displaying the white over the entire area in the sub-frame period SF _2. Note that, in the first frame period and the second frame period, the subframe periods SF _1, displays a pattern in which a white region and the black region are inverted to each other. Then, two frame periods appeared alternately, and the presence or absence of a pseudo contour was examined.

When the ratio of the subframe periods SF ₁ was _R 1 (%) in one frame _period, for _R 1 (%), the value of the minimum frame frequency F which generation of a pseudo contour is observed (Hz) is 2 The relationship is as shown. As can be seen from FIG. 2, the lower the R ₁ (%), the lower the lowest frame frequency F (Hz) at which the occurrence of a pseudo contour is recognized. Conversely, the higher the R ₁ (%), the higher the lowest frame frequency F (Hz) at which the occurrence of a pseudo contour is recognized.

Therefore, as the display of each pixel is short different subframe periods SF ₁ for each frame period, it can be said that a pseudo contour is less likely to occur. Conversely, the longer sub-frame period SF ₂ displayed at each pixel in the adjacent frame periods are the same is true with false contour hardly occurs. Therefore, from the results of the above experiment, it was found that the generation of pseudo contours can be suppressed as the ratio of the length of the subframe periods that are in the light emission state (sharing rate) is higher in the adjacent frame periods.

FIG. 14 illustrates an example of a configuration of a subframe period used in an actual light emitting device. FIG. 14 (A) shows the configuration of the sub-frame period of the tone 7 at the time of performing the display of the total gray scale level 2 ^4, the configuration of the sub-frame period of gradation 8. In FIG. 14A, four subframe periods SF _{1 to} SF ₄ are used, and the subframe period SF ₄ is further divided into two. The ratio of the lengths of the subframe periods SF _{1 to} SF ₄ is SF1: SF2: SF3: SF4 = 1: 2: 4: 8. Further, the period indicated by BK corresponds to a period (non-display period) in which the light emitting element is forced to be in a non-light emitting state, and thus does not contribute to gradation.

In the case of displaying gradation 7 in FIG. 14A, the subframe periods in the light emitting state are SF ₁ , SF ₂ , SF ₃ , and the subframe periods in the non-light emitting state are SF ₄ . On the other hand, in the case of displaying gradation 8 in FIG. 14A, the subframe period in the light emitting state is SF ₄ , and the subframe periods in the non-light emitting state are SF ₁ , SF ₂ , and SF ₃ . Therefore, since there is no subframe period in which both are in a light emitting state, the sharing rate is 0%. Therefore, it can be said that a pseudo contour is likely to occur in the configuration of the subframe period illustrated in FIG.

Next, FIG. 14B illustrates a structure of a subframe period different from that in FIG. Figure 14 (B), like the FIG. 14 (A), the shown configuration of the sub-frame period of the tone 7 at the time of performing the display of the total gray scale level 2 ^4, the configuration of the sub-frame period of gradation 8 ing. In FIG. 14B, eight subframe periods SF _{1 to} SF ₈ are used. The ratio of the lengths of the subframe periods SF _{1 to} SF ₈ is SF1: SF2: SF3: SF4: SF5: SF6: SF7: SF8 = 1: 1: 1: 2: 2: 2: 3: 3. Yes. Note that the period indicated by BK corresponds to a non-display period and thus does not contribute to gradation.

In the case of displaying gradation 7 in FIG. 14B, SF ₃ , SF ₇ , SF ₈ are subframe periods in the light emission state, and SF ₁ , SF ₂ , SF ₄ are subframe periods in the non-light emission state. , SF ₅ , SF ₆ . On the other hand, when gray scale 8 is displayed in FIG. 14B, the subframe periods in the light emitting state are SF ₆ , SF ₇ , SF ₈ , and the subframe periods in the non-light emitting state are SF ₁ , SF ₂ , SF ₃ , SF ₄ , and SF ₅ . Therefore, since the subframe periods in which both are in the light emission state are SF ₇ and SF ₈ , the sharing rate is (SF ₇ + SF ₈ ) × 100 / (SF ₆ + SF ₇ + SF ₈ ) = 75%. Therefore, it can be said that the configuration of the subframe period illustrated in FIG. 14B is less likely to generate a pseudo contour than the case of FIG.

Next, in carrying out the driving method of the present invention, a method for determining the length of each subframe period appearing in one frame period from the sharing rate R _sh and the total number of gradations will be specifically described.

First, the sharing rate R _sh is obtained from the frame frequency used for driving. The false contour is less likely to be generated as the frame frequency is higher, and conversely, it is more likely to be generated as the frame frequency is lower. Therefore, if the frame frequency is determined in advance, the lowest sharing rate that will be able to suppress the generation of the pseudo contour can be determined for each light emitting device.

FIG. 3 shows, as an example, the relationship between the frame frequency (Hz) and the lowest sharing rate (%) that can suppress the occurrence of a pseudo contour. The sharing rate (%) corresponds to 100 (%)-R ₁ (%). As shown in FIG. 3, the lower the sharing rate, the higher the frame frequency is required to suppress the occurrence of pseudo contours. Note that since the practitioner can appropriately determine whether or not the pseudo contour has occurred, the same relationship as in FIG. 3 is not necessarily derived. However, under a certain set criterion, the higher the frame frequency, the more the generation of pseudo contour can be suppressed, and the generation of the pseudo contour can be suppressed. The relationship with the lowest share (%) can be derived.

From the graph shown in FIG. 3, when the lowest sharing rate (%) that can suppress the occurrence of pseudo contours when a specific frame frequency is used is derived, it is equal to or higher than the sharing rate. A sharing rate R _sh having a value of can be determined. Once the sharing rate R _sh is determined, the length of each subframe period is determined from the sharing rate R _sh .

First, let n subframe periods included in one frame period be SF _{1 to} SF _{n in} order from the shortest. Here, n is an integer of 2 or more. Then, it is assumed that gradation m (m <2 ⁿ ) can be displayed when all of SF _{1 to} SF _p (p <n) are emitted. In this case, the sub-frame periods SF ₁ - SF _p that emits light when displaying the gradation m, and the length of the total of the T _m, T _m can be expressed by Equation 1 below.

Next, consider the case of displaying gradation (m + 1). Since gradation m can be displayed when all of SF _{1 to} SF _p are caused to emit light, it is necessary to use SF _{p + 1} longer than SF _{p in} order to display gradation (m + 1). At the same time, _one or a plurality of subframe periods corresponding to a value obtained by subtracting a length corresponding to one gradation (for example, a length corresponding to SF ₁ ) from SF _{p + 1} is displayed by removing from SF _{1 to} SF _p. It is necessary to do. Therefore, if the total length of the subframe periods that emit light when displaying the gradation (m + 1) is T _{m + 1} , T _{m + 1} can be expressed by Equation 2 below.

Here, the proportion of _{SF p + 1} to the sum of subframe periods _{SF 1 ~SF p +} 1, when the sub-frame rate _{R SF, R SF} can be expressed by Equation 3 below.

  From Equation 3, the following Equation 4 can be derived.

Further, when the total length of the sub-frame periods in which both the gray scale m is displayed and the gray scale (m + 1) is displayed is W _{m / m + 1} , W _{m / m + 1} is as follows. It can be expressed by Equation 5.

  Therefore, the following Expression 6 is derived from Expression 1, Expression 4, and Expression 5.

Further, the sharing rate R _sh of the sub-frame period in which both the gray level m is displayed and the gray level (m + 1) is displayed is expressed by the following Expression 7.

  Therefore, the following Expression 8 is derived from Expression 2, Expression 4, Expression 6, and Expression 7.

  Therefore, from Equation 8, the following Equation 9 can be derived.

Therefore, the value of the subframe rate R _SF can be derived by substituting the value of the sharing rate R _sh into Equation 9. Subframe ratio _{R SF} is the ratio of the _{SF p + 1} to the sum of subframe periods _{SF 1 ~SF p +} 1. By using the sub-frame rate R _SF, in order from the longest sub-frame period SF _n, it is possible to determine the length of each sub-frame period.

In the present embodiment, an example in which a constant subframe rate R _SF is applied from SF _n to SF ₁ is shown, but the present invention is not limited to this configuration. For example, even when a display with a total number of gradations of 2 ^{n is performed,} the number of subframe periods is not necessarily n. When the length calculated according to Equation 9 is reflected in each subframe period, the number of subframe periods is often n or more. However, a short subframe period for displaying a low gradation does not necessarily contribute to the generation of a pseudo contour even if it does not necessarily satisfy the value of the sharing rate R _sh described above. This is because, in the case of a low gradation, the reciprocal of the gradation × 100 (gradation ratio) is larger than that in the case of a high gradation, so that the contour due to the difference in gradation is visually recognized, and conversely the pseudo contour is This is because it doesn't stand out.

  FIG. 13 is a graph showing the relationship between the gradation ratio (%) and the lowest frame frequency F (Hz) at which the occurrence of a pseudo contour is recognized. In FIG. 13, the horizontal axis represents the gradation ratio (%), and the vertical axis represents the lowest frame frequency F (Hz) at which the occurrence of a pseudo contour is recognized. From FIG. 13, it can be seen that the higher the gradation ratio (%), that is, the lower the gradation, the more the pseudo contour can be suppressed even at a lower frame frequency.

  Therefore, in order to place more emphasis on the reduction of the driving frequency of the driving circuit rather than creating more subframe periods that are not involved in the generation of the pseudo contour, it is possible to thin out the subframe periods having a short period. Specifically, when there are a plurality of subframe periods having a short period corresponding to gradation 1 in the calculation, one or some of them are thinned out.

Specifically, the total number of gradations is divided into three equal parts, and the value of the sharing rate R _sh does not necessarily have to be satisfied in the lowest gradation among the three divided total number of gradations. On the contrary, among the total number of gradations divided into three, the value of the sharing rate R _sh is satisfied in the intermediate gradation and the highest gradation. For example, when the total number of gradations is 2 ⁶ = 64, 21 is obtained by dividing the gradations 0 to 63 into three equal parts. In this case, the lower gradation is 0 to 21, the intermediate gradation is 22 to 42, and the highest gradation is 43 to 63. If the total number of tones is not evenly divided by three, the fraction may be rounded up or down.

4, an example in which to display the total gray scale level is 2 ⁴ using 4-bit video signal, indicating the sub-frame period, the relationship between the gradation in the state of light emission. In FIG. 4, the horizontal axis corresponds to the total length (light emission period) of the subframe periods in which the gray scale is on the left and the left vertical axis is in the light emission state. The gradation to be displayed is determined by the length of the light emission period. Similarly, FIG. 4 also shows the sharing ratio R _sh (%) when compared with the case where the gradation is lower by one level on the right vertical axis. FIG. 4 shows an example in which display is performed using _nine subframe periods SF _{1 to} SF ₉ . The ratio of the lengths of the subframe periods SF _{1 to} SF ₉ is 1: 1: 1: 1: 1: 2: 2: 3: 3 in order from SF ₁ .

In FIG. 4, the length of each subframe period is determined so that the sharing rate R _sh (%) is maintained at 65% or more when displaying gradations 3 to 15. Incidentally, the definition of the sharing ratio _{R sh,} the gradation 0,1, sharing ratio _R sh (%) is not satisfied. In FIG. 4, the sharing rate R _sh (%) is not satisfied at the relatively low gradation 2. However, since a pseudo contour is unlikely to occur at a low gradation, it is not always necessary to satisfy the sharing rate R _sh (%).

FIG. 15 shows an example in which a total number of gradations of ²⁶ is displayed using a 6-bit video signal, and shows the relationship between the subframe period in the light emission state and the gradation. In FIG. 15, the horizontal axis corresponds to the total length (light emission period) of subframe periods in which the gray scale is on the left and the left vertical axis is in the light emission state. The gradation to be displayed is determined by the length of the light emission period. Similarly, FIG. 15 also shows the sharing ratio R _sh (%) when compared with the case where the gradation is lower by one step on the right vertical axis. Note that FIG. 15 shows an example in which display is performed using ₁₂ subframe periods SF _{1 to} SF ₁₂ . The ratio of the lengths of the subframe periods SF _{1 to} SF ₁₂ is 1: 2: 3: 3: 4: 4: 5: 6: 7: 8: 9: 11 in order from SF ₁ .

In FIG. 15, the length of each subframe period is determined so that the sharing rate R _sh (%) is maintained at 70% or higher when displaying the gradations 12 to 63. Incidentally, the definition of the sharing ratio _{R sh,} the gradation 0,1, sharing ratio _R sh (%) is not satisfied. In FIG. 15, the sharing rate R _sh (%) is not satisfied at the relatively low gradations 2 to 11. However, since a pseudo contour is unlikely to occur at a low gradation, it is not always necessary to satisfy the sharing rate R _sh (%).

  Note that in the driving method of the present invention, the light emission state or the non-light emission state in each subframe period is controlled by referring to a table that defines the relationship between the gradation of the video signal and the light emitting subframe period. Table 1 shows the relationship between the gradation of the video signal and the light emission or non-light emission state in each subframe period in the case of FIG.

Table 1 corresponds to a table indicating the relationship between a 4-bit video signal and nine subframe periods, and the light emission state or non-light emission state in each of the subframe periods SF _{1 to} SF ₉ is determined according to the table. Be controlled. In Table 1, “◯” represents a light emission state, and “x” represents a non-light emission state. As described above, in the present invention, a video signal is converted in accordance with data as shown in Table 1, and display is performed using the converted video signal.

  Note that the light-emitting device that performs the above-described driving method of the present invention has a table that outputs a signal determined in response to a signal input. The table is configured by a memory such as a ROM or a RAM as hardware, and stores data as shown in Table 1, for example. Of course, the data of the table is not limited to Table 1, but can be arbitrarily provided according to the total number of gradations of the image to be displayed and the number or length of the subframe periods.

  Next, a specific configuration of the light emitting device of the present invention will be described. FIG. 5A illustrates an example of a structure of the light-emitting device of the present invention in a block diagram. The light emitting device illustrated in FIG. 5 includes a panel 101, a controller 102, and a table 103. Further, the panel 101 includes a pixel portion 104 having a light emitting element in each pixel, a signal line driver circuit 105, and a scanning line driver circuit 106.

The table 103 is configured by a memory such as a ROM or a RAM as hardware. In the memory, the number and length of a plurality of subframe periods included in one frame period according to the subframe rate R _SF , and a subframe period in which light is emitted among the plurality of subframe periods in each gradation are stored. Data for setting is stored. The subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency.

In accordance with the data stored in the table 103, the controller 102 can determine the subframe period in which the light emission is performed according to the gradation of the input video signal. Specifically, according to Table 1, for example, when the gradation of the video signal is 10, the subframe periods in which light is emitted are SF _{1 to} SF ₆ and SF ₈ . In addition, the controller 102 includes a frame memory, and a clock signal in accordance with the length of each of a plurality of subframe periods stored in the table 103, the driving frequency of the signal line driver circuit 105 or the scanning line driver circuit 106, and the like. Various control signals such as a start pulse signal can be generated.

  Note that although FIG. 5A illustrates an example in which the video signal conversion and the control signal generation are both performed by the controller 102, the present invention is not limited to this configuration. A controller that converts video signals and a controller that generates control signals may be provided separately in the light emitting device.

  FIG. 5B illustrates an example of a more specific structure of the panel 101 illustrated in FIG.

  In FIG. 5B, the signal line driver circuit 105 includes a shift register 110, a latch A111, and a latch B112. Various control signals such as a clock signal (CLK) and a start pulse signal (SP) are input to the shift register 110. When the clock signal (CLK) and the start pulse signal (SP) are input, a timing signal is generated in the shift register 110. The generated timing signals are sequentially input to the first-stage latch A111. When the timing signal is input to the latch A111, the video signal input from the controller 102 is sequentially written and held in the latch A111 in synchronization with the pulse of the timing signal. In this embodiment, video signals are sequentially written in the latch A111, but the present invention is not limited to this configuration. A plurality of stages of latches A111 may be divided into several groups, and so-called divided driving may be performed in which video signals are input in parallel for each group. Note that the number of groups at this time is called the number of divisions. For example, when the latches are divided into groups every four stages, it can be said that the driving is divided into four.

  A period until video signal writing to the latches of all stages of the latch A111 is completed is called a row selection period. Actually, the row selection period may include a period in which a horizontal blanking period is added to the row selection period.

  When one row selection period ends, a latch signal (Latch Signal) corresponding to one of the control signals is supplied to the second-stage latch B112, and the video signal held in the latch A111 in synchronization with the latch signal Are simultaneously written to the latch B112. In the latch A111 that has finished sending the video signal to the latch B112, the video signal of the next bit is sequentially written in synchronization with the timing signal from the shift register 110 again. During this second row selection period, the video signal written and held in the latch B 112 is input to the pixel portion 104.

  Instead of the shift register 110, another circuit capable of selecting a signal line such as a decoder may be used.

  Next, the configuration of the scanning line driving circuit 106 will be described. The scan line driver circuit 106 includes a shift register 113 and a buffer 114. In some cases, a level shifter may be provided. In the scan line driver circuit 106, when the clock signal (CLK) and the start pulse signal (SP) are input to the shift register 113, a selection signal is generated. The generated selection signal is amplified in the buffer 114 and supplied to the corresponding scanning line. Since the operation of the transistors included in the pixels for one row is controlled by the selection signal supplied to the scan line, a buffer 114 that can supply a relatively large current to the scan line is used. It is desirable.

  Instead of the shift register 113, another circuit capable of selecting a signal line such as a decoder may be used.

  In the present invention, the scanning line driver circuit 106 and the signal line driver circuit 105 may be formed on the same substrate as the pixel portion 104 or on a different substrate. In addition, the panel included in the light-emitting device of the present invention is not limited to the structure shown in FIGS. The panel 101 only needs to have a configuration in which the gradation of the pixel is controlled in accordance with the video signal input from the controller 102.

  Next, a circuit diagram of a pixel included in the light-emitting device of the present invention will be described with reference to FIG.

  FIG. 6A illustrates an example of an equivalent circuit diagram of a pixel, which includes a signal line 6114, a power supply line 6115, a scanning line 6116, a light-emitting element 6113, TFTs 6110 and 6111, and a capacitor element 6112. A video signal is input to the signal line 6114 by a signal line driver circuit. The TFT 6110 can control supply of the potential of the video signal to the gate of the TFT 6111 in accordance with a selection signal input to the scan line 6116. The TFT 6111 can control supply of current to the light-emitting element 6113 in accordance with the potential of the video signal. The capacitor 6112 can hold the voltage between the gate and the source of the TFT 6111. Note that although the capacitor 6112 is illustrated in FIG. 6A, the capacitor 6112 is not necessarily provided when it can be covered by the gate capacitance of the TFT 6111 or other parasitic capacitance.

  FIG. 6B is an equivalent circuit diagram of a pixel in which a TFT 6118 and a scanning line 6119 are newly provided in the pixel shown in FIG. With the TFT 6118, the gate and the source of the TFT 6111 can be set to the same potential, and a state in which no current flows through the light-emitting element 6113 can be forcibly created. Therefore, the subframe period is longer than the period in which video signals are input to all pixels. The length can be shortened. Therefore, display with a high total number of gradations can be performed while suppressing the drive frequency.

  FIG. 6C is an equivalent circuit diagram of a pixel in which a TFT 6125 and a wiring 6126 are newly provided in the pixel illustrated in FIG. The gate of the TFT 6125 is fixed by a wiring 6126. The TFT 6111 and the TFT 6125 are connected in series between the power supply line 6115 and the light emitting element 6113. Therefore, in FIG. 6C, the value of the current supplied to the light-emitting element 6113 by the TFT 6125 is controlled, and whether or not the current is supplied to the light-emitting element 6113 can be controlled by the TFT 6111.

  Note that the pixel included in the light-emitting device of the present invention is not limited to the structure shown in this embodiment. This embodiment can be freely combined with the above embodiment modes.

  In this embodiment, the driving method shown in FIG. 4 is taken as an example, and the timing at which each subframe period appears will be described.

FIG. 7 shows a timing chart in the case of displaying 4-bit gradation using the driving method shown in FIG. In FIG. 7, the horizontal axis indicates the lengths of the subframe periods SF _{1 to} SF ₉ that appear in one frame period, and the vertical axis indicates the scanning line selection order. The ratio of the lengths of the subframe periods SF _{1 to} SF ₉ is 1: 1: 1: 1: 1: 2: 2: 3: 3 in order from SF ₁ .

  When each subframe period starts, video signals are input for each row of pixels sharing a scan line. When a video signal is input to a pixel, the light-emitting element enters a light-emitting state or a non-light-emitting state in accordance with information included in the video signal. Then, until the next subframe period starts, the light emitting element of each pixel maintains a light emitting state or a non-light emitting state according to the video signal.

  Note that FIG. 7 illustrates a timing chart in the case where the light-emitting element is in a light-emitting state or a non-light-emitting state in accordance with information included in the video signal at the same time as the video signal is input to the pixel. It is not limited to this configuration. Until the video signal is input to all the pixels, the light emitting element is in a non-light emitting state. After the video signal is input to all the pixels, the light emitting element is turned on or off according to the information included in the video signal. It may be in a non-light emitting state.

  Further, FIG. 7 shows a timing chart when all subframe periods appear continuously, but the present invention is not limited to this configuration. A period (non-display period) in which the light-emitting element is forcibly brought into a non-light-emitting state may be provided between the sub-frame period and the sub-frame period. The non-display period may appear after the video signal is input to all the pixels in the subframe period that appears immediately before the non-display period, or may appear before the video signal is input to all the pixels. May be.

  In this embodiment, a cross-sectional structure of a pixel in the case where a transistor for controlling current supply to a light-emitting element is a p-type will be described with reference to FIGS. Note that in this specification, of the two electrodes of the anode and the cathode included in the light-emitting element, one electrode whose potential can be controlled by a transistor is a first electrode, and the other electrode is a second electrode. 8 illustrates the case where the first electrode is an anode and the second electrode is a cathode, the first electrode may be a cathode and the second electrode may be an anode.

  FIG. 8A is a cross-sectional view of a pixel in the case where the transistor 6001 is p-type and light emitted from the light-emitting element 6003 is extracted from the first electrode 6004 side. In FIG. 8A, the first electrode 6004 of the light-emitting element 6003 and the transistor 6001 are electrically connected.

  The transistor 6001 is covered with an interlayer insulating film 6007, and a partition wall 6008 having an opening is formed over the interlayer insulating film 6007. A part of the first electrode 6004 is exposed in the opening of the partition wall 6008, and the first electrode 6004, the electroluminescent layer 6005, and the second electrode 6006 are sequentially stacked in the opening.

  The interlayer insulating film 6007 is formed using an organic resin film, an inorganic insulating film, or an insulating film including a Si—O—Si bond (hereinafter referred to as a siloxane-based insulating film) formed using a siloxane-based material as a starting material. Can do. Siloxane is composed of a Si—O bond skeleton, and the substituent contains an organic group containing at least hydrogen (such as an alkyl group or an aromatic hydrocarbon group). Note that a fluoro group or a fluoro group and an organic group containing at least hydrogen may be used as a substituent. A material called a low dielectric constant material (low-k material) may be used for the interlayer insulating film 6007.

  The partition wall 6008 can be formed using an organic resin film, an inorganic insulating film, or a siloxane-based insulating film. For example, acrylic resin, polyimide, polyamide, or the like can be used for the organic resin film, and silicon oxide, silicon nitride oxide, or the like can be used for the inorganic insulating film. In particular, a photosensitive organic resin film is used for the partition wall 6008, an opening is formed on the first electrode 6004, and the side wall of the opening is formed as an inclined surface formed with a continuous curvature. Thus, the connection between the first electrode 6004 and the second electrode 6006 can be prevented.

  The first electrode 6004 is formed using a light-transmitting material or film thickness, and is formed using a material suitable for use as an anode. For example, another light-transmitting oxide conductive material such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), or zinc oxide added with gallium (GZO) is used for the first electrode 6004. Is possible. A conductive film formed using a target in which indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide is further mixed with 2 to 20 wt% zinc oxide (ZnO). May be used for the first electrode 6004. In addition to the light-transmitting oxide conductive material, for example, a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and aluminum are used. The first electrode 6004 can be formed using a stack including a main component film, a three-layer structure including a titanium nitride film, an aluminum main component film, and a titanium nitride film. Note that in the case where a material other than the light-transmitting oxide conductive material is used, the first electrode 6004 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm).

The second electrode 6006 can be formed using a material and a film thickness that reflect or shield light, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used.

  The electroluminescent layer 6005 is composed of one or more layers. When composed of a plurality of layers, these layers can be classified into a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like from the viewpoint of carrier transport characteristics. In the case where the electroluminescent layer 6005 includes any of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer, the first electrode 6004 to the positive hole injection layer, A hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are laminated in this order. Note that the boundaries between the layers are not necessarily clear, and there are cases where the materials constituting the layers are partially mixed and the interface is unclear. For each layer, an organic material or an inorganic material can be used. As the organic material, any of a high molecular weight material, a medium molecular weight material, and a low molecular weight material can be used. The medium molecular weight material corresponds to a low polymer having a number of repeating structural units (degree of polymerization) of about 2 to 20. The distinction between a hole injection layer and a hole transport layer is not necessarily strict, and these are the same in the sense that hole transportability (hole mobility) is a particularly important characteristic. For convenience, the hole injection layer is a layer in contact with the anode, and the layer in contact with the hole injection layer is referred to as a hole transport layer to be distinguished. The same applies to the electron transport layer and the electron injection layer. The layer in contact with the cathode is called an electron injection layer, and the layer in contact with the electron injection layer is called an electron transport layer. The light emitting layer may also serve as an electron transport layer, and is also referred to as a light emitting electron transport layer.

  In the case of the pixel shown in FIG. 8A, light emitted from the light-emitting element 6003 can be extracted from the first electrode 6004 side as shown by a hollow arrow.

  Next, FIG. 8B is a cross-sectional view of a pixel in the case where the transistor 6011 is p-type and light emitted from the light-emitting element 6013 is extracted from the second electrode 6016 side. In FIG. 8B, the first electrode 6014 of the light-emitting element 6013 and the transistor 6011 are electrically connected. In addition, an electroluminescent layer 6015 and a second electrode 6016 are sequentially stacked over the first electrode 6014.

  The first electrode 6014 is formed using a material and a film thickness that reflect or shield light, and is formed using a material that is suitable for use as an anode. For example, in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., a laminate of titanium nitride and a film containing aluminum as a main component, a titanium nitride film A three-layer structure of a film mainly containing aluminum and aluminum and a titanium nitride film can be used for the first electrode 6014.

The second electrode 6016 can be formed using a light-transmitting material or film thickness, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used. Then, the second electrode 6016 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Note that other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide to which gallium is added (GZO) can also be used. A conductive film formed using a target in which indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide is further mixed with 2 to 20 wt% zinc oxide (ZnO). May be used. In the case of using a light-transmitting oxide conductive material, it is preferable to provide an electron injection layer in the electroluminescent layer 6015.

  The electroluminescent layer 6015 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG.

  In the case of the pixel shown in FIG. 8B, light emitted from the light-emitting element 6013 can be extracted from the second electrode 6016 side as shown by a hollow arrow.

  Next, FIG. 8C is a cross-sectional view of a pixel in the case where the transistor 6021 is p-type and light emitted from the light-emitting element 6023 is extracted from the first electrode 6024 side and the second electrode 6026 side. In FIG. 8C, the first electrode 6024 of the light-emitting element 6023 and the transistor 6021 are electrically connected. Further, an electroluminescent layer 6025 and a second electrode 6026 are sequentially stacked over the first electrode 6024.

  The first electrode 6024 can be formed in a manner similar to that of the first electrode 6004 in FIG. The second electrode 6026 can be formed in a manner similar to that of the second electrode 6016 in FIG. The electroluminescent layer 6025 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG.

  In the case of the pixel shown in FIG. 8C, light emitted from the light-emitting element 6023 can be extracted from the first electrode 6024 side and the second electrode 6026 side as indicated by white arrows.

  This embodiment can be freely combined with the above embodiment modes and embodiments.

  In this embodiment, a cross-sectional structure of a pixel in the case where an n-type transistor is described with reference to FIGS. Note that although FIG. 9 illustrates the case where the first electrode is a cathode and the second electrode is an anode, the first electrode may be an anode and the second electrode may be a cathode.

  FIG. 9A is a cross-sectional view of a pixel in the case where the transistor 6031 is n-type and light emitted from the light-emitting element 6033 is extracted from the first electrode 6034 side. In FIG. 9A, the first electrode 6034 of the light-emitting element 6033 and the transistor 6031 are electrically connected. Further, an electroluminescent layer 6035 and a second electrode 6036 are sequentially stacked over the first electrode 6034.

The first electrode 6034 can be formed using a light-transmitting material or film thickness, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used. Then, the first electrode 6034 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm). Further, a light-transmitting conductive layer is formed using a light-transmitting oxide conductive material so as to be in contact with or under the conductive layer having a thickness enough to transmit light, and the first electrode 6034 is formed. The sheet resistance may be suppressed. Note that only conductive layers using other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide added with gallium (GZO) should be used. Is also possible. A conductive film formed using a target in which indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide is further mixed with 2 to 20 wt% zinc oxide (ZnO). May be used. In the case of using a light-transmitting oxide conductive material, it is preferable to provide an electron injection layer in the electroluminescent layer 6035.

  The second electrode 6036 is formed of a material and a film thickness that reflect or shield light, and is formed using a material that is suitable for use as an anode. For example, in addition to a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., a laminate of titanium nitride and a film containing aluminum as a main component, a titanium nitride film A three-layer structure of a film containing aluminum and aluminum as main components and a titanium nitride film can be used for the second electrode 6036.

  The electroluminescent layer 6035 can be formed in a manner similar to that of the electroluminescent layer 6005 in FIG. However, in the case where the electroluminescent layer 6035 includes any one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer, the first electrode 6034 to the electron injection layer The electron transport layer, the light emitting layer, the hole transport layer, and the hole injection layer are laminated in this order.

  In the case of the pixel shown in FIG. 9A, light emitted from the light-emitting element 6033 can be extracted from the first electrode 6034 side as shown by a hollow arrow.

  Next, FIG. 9B is a cross-sectional view of a pixel in the case where the transistor 6041 is an n-type transistor and light emitted from the light-emitting element 6043 is extracted from the second electrode 6046 side. In FIG. 9B, the first electrode 6044 of the light-emitting element 6043 and the transistor 6041 are electrically connected. Further, an electroluminescent layer 6045 and a second electrode 6046 are sequentially stacked over the first electrode 6044.

The first electrode 6044 can be formed using a material and a film thickness that reflect or shield light, and can be formed using a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like with a low work function. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. When an electron injection layer is provided, other conductive layers such as Al can be used.

  The second electrode 6046 is formed using a light-transmitting material or film thickness, and is formed using a material suitable for use as an anode. For example, another light-transmitting oxide conductive material such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), or zinc oxide added with gallium (GZO) is used for the second electrode 6046. Is possible. A conductive film formed using a target in which indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide is further mixed with 2 to 20 wt% zinc oxide (ZnO). May be used for the second electrode 6046. In addition to the light-transmitting oxide conductive material, for example, a single layer film made of one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and aluminum are used. The second electrode 6046 can be formed using a stack of a main component film, a three-layer structure including a titanium nitride film, an aluminum main component film, and a titanium nitride film. Note that in the case where a material other than the light-transmitting oxide conductive material is used, the second electrode 6046 is formed with a thickness enough to transmit light (preferably, about 5 nm to 30 nm).

  The electroluminescent layer 6045 can be formed in a manner similar to that of the electroluminescent layer 6035 in FIG.

  In the case of the pixel shown in FIG. 9B, light emitted from the light-emitting element 6043 can be extracted from the second electrode 6046 side as shown by a hollow arrow.

  Next, FIG. 9C is a cross-sectional view of a pixel in the case where the transistor 6051 is n-type and light emitted from the light-emitting element 6053 is extracted from the first electrode 6054 side and the second electrode 6056 side. In FIG. 9C, the first electrode 6054 of the light-emitting element 6053 and the transistor 6051 are electrically connected. Further, an electroluminescent layer 6055 and a second electrode 6056 are stacked over the first electrode 6054 in this order.

  The first electrode 6054 can be formed in a manner similar to that of the first electrode 6034 in FIG. The second electrode 6056 can be formed in a manner similar to that of the second electrode 6046 in FIG. The electroluminescent layer 6055 can be formed in a manner similar to that of the electroluminescent layer 6035 in FIG.

  In the case of the pixel shown in FIG. 9C, light emitted from the light-emitting element 6053 can be extracted from the first electrode 6054 side and the second electrode 6056 side as indicated by white arrows.

  This embodiment can be freely combined with the above embodiment modes and embodiments.

  The light-emitting device of the present invention can be formed by a screen printing method, a printing method typified by an offset printing method, or a droplet discharge method. The droplet discharge method means a method of forming a predetermined pattern by discharging droplets containing a predetermined composition from the pores, and includes an ink jet method and the like in its category. By using the above printing method and droplet discharge method, various wirings typified by signal lines, scanning lines, selection lines, TFT gates, and light emitting element electrodes can be formed without using an exposure mask. Is possible. However, it is not necessary to use a printing method or a droplet discharge method for all the steps of forming a pattern. Therefore, for example, a printing method or a droplet discharge method is used in at least a part of the process such that a printing method or a droplet discharge method is used for forming a wiring and a gate, and a lithography method is used for patterning a semiconductor film. As long as it is, a lithography method may be used in combination. The mask used for patterning may be formed by a printing method or a droplet discharge method.

  FIG. 10 shows an example of a cross-sectional view of a light-emitting device of the present invention formed using a droplet discharge method. In FIG. 10, 1301 and 1302 correspond to transistors, and 1304 corresponds to a light emitting element. The transistor 1302 is electrically connected to the first electrode 1350 of the light-emitting element 1304. The transistor 1302 is preferably n-type. In this case, the first electrode 1350 is preferably a cathode, and the second electrode 1331 is preferably an anode.

  The transistor 1301 functioning as a switching element includes a gate 1310, a first semiconductor film 1311 including a channel formation region, a gate insulating film 1317 formed between the gate 1310 and the first semiconductor film 1311, and a source or drain. Second semiconductor films 1312 and 1313 functioning as a wiring, a wiring 1314 connected to the second semiconductor film 1312, and a wiring 1315 connected to the second semiconductor film 1313.

  The transistor 1302 includes a gate 1320, a first semiconductor film 1321 including a channel formation region, a gate insulating film 1317 formed in the gate 1320 and the first semiconductor film 1321, and a second semiconductor functioning as a source or a drain. Films 1322 and 1323, a wiring 1324 connected to the second semiconductor film 1322, and a wiring 1325 connected to the second semiconductor film 1323 are included.

  The wiring 1314 corresponds to a signal line, and the wiring 1315 is electrically connected to the gate 1320 of the transistor 1302. The wiring 1325 corresponds to a power supply line.

  By forming a pattern using a droplet discharge method or a printing method, a series of steps such as photoresist film formation, exposure, development, etching, and peeling performed by a lithography method can be simplified. Further, unlike the lithography method, the droplet discharge method and the printing method do not waste material that is removed by etching. Further, it is not necessary to use an expensive exposure mask, so that the cost for manufacturing the light-emitting device can be suppressed.

  Further, unlike the lithography method, it is not necessary to perform etching to form the wiring. Therefore, the time spent for the process of forming the wiring can be significantly shortened compared to the case of the lithography method. In particular, when the wiring thickness is 0.5 μm or more, and more desirably 2 μm or more, the wiring resistance can be suppressed. Therefore, the wiring accompanying the increase in the size of the light-emitting device while suppressing the time spent in the wiring manufacturing process. An increase in resistance can be suppressed.

  Note that the first semiconductor films 1311 and 1321 may be either an amorphous semiconductor or a semi-amorphous semiconductor (SAS).

An amorphous semiconductor can be obtained by glow discharge decomposition of a silicide gas. Typical silicide gases include SiH ₄ and Si ₂ H ₆ . This silicide gas may be diluted with hydrogen, hydrogen and helium.

SAS can also be obtained by glow discharge decomposition of silicide gas. A typical silicide gas is SiH ₄ , and Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4, and the} like can be used. In addition, it is easy to form a SAS by diluting and using this silicide gas with hydrogen or a gas obtained by adding one or more kinds of rare gas elements selected from helium, argon, krypton, and neon to hydrogen. It can be. It is preferable to dilute the silicide gas at a dilution rate in the range of 2 to 1000 times. Furthermore, carbide gas such as CH ₄ and C ₂ H ₆ , germanium gas such as GeH ₄ and GeF ₄ , F _{2 and the} like are mixed in the silicide gas, and the energy bandwidth is 1.5-2. You may adjust to 4 eV or 0.9-1.1 eV. A TFT using SAS as the first semiconductor film can obtain a mobility of 1 to 10 cm ² / Vsec or more.

  The first semiconductor films 1311 and 1321 may be formed using a semiconductor obtained by laser crystallization of an amorphous semiconductor or a semi-amorphous semiconductor (SAS).

  This embodiment can be freely combined with the above embodiment modes and embodiments.

  In this example, the appearance of a panel corresponding to one embodiment of the light-emitting device of the present invention will be described with reference to FIG. FIG. 11 is a top view of a panel in which a transistor and a light-emitting element formed over the first substrate are sealed with a sealant between the second substrate and FIG. 11B. This corresponds to a cross-sectional view taken along line AA ′ in FIG.

  A sealant 4005 is provided so as to surround the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 which are provided over the first substrate 4001. In addition, a second substrate 4006 is provided over the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004. Therefore, the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 are sealed together with the filler 4007 by the first substrate 4001, the sealant 4005, and the second substrate 4006.

  In addition, the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 provided over the first substrate 4001 include a plurality of transistors. In FIG. A transistor 4008 included in 4003 and a transistor 4009 included in the pixel portion 4002 are illustrated.

  4011 corresponds to a light-emitting element, and part of the wiring 4017 connected to the drain of the transistor 4009 functions as the first electrode of the light-emitting element 4011. The transparent conductive film 4012 functions as the second electrode of the light-emitting element 4011. Note that the structure of the light-emitting element 4011 is not limited to the structure shown in this embodiment. The structure of the light-emitting element 4011 can be changed as appropriate depending on the direction of light extracted from the light-emitting element 4011, the polarity of the transistor 4009, or the like.

  Further, various signals and voltages supplied to the signal line driver circuit 4003, the scan line driver circuit 4004, or the pixel portion 4002 are not shown in the cross-sectional view in FIG. 11B, but are routed through lead wirings 4014 and 4015. It is supplied from the connection terminal 4016.

  In this embodiment, the connection terminal 4016 is formed using the same conductive film as the first electrode included in the light-emitting element 4011. Further, the lead wiring 4014 is formed of the same conductive film as the wiring 4017. The lead wiring 4015 is formed using the same conductive film as the gates of the transistors 4009 and 4008.

  The connection terminal 4016 is electrically connected to a terminal included in the FPC 4018 through an anisotropic conductive film 4019.

  Note that as the first substrate 4001 and the second substrate 4006, glass, metal (typically stainless steel), ceramics, or plastic can be used. As the plastic, an FRP (Fiberglass-Reinforced Plastics) plate, a PVF (polyvinyl fluoride) film, a mylar film, a polyester film, or an acrylic resin film can be used. A sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can also be used.

  Note that the second substrate 4006 must have a light-transmitting property with respect to the substrate positioned in the light extraction direction from the light-emitting element 4011. In that case, a light-transmitting material such as a glass plate, a plastic plate, a polyester film, or an acrylic film is used.

  As the filler 4007, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicon resin, PVB (Polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.

  This embodiment can be freely combined with the above embodiment modes and embodiments.

  Since the semiconductor display device of the present invention can suppress the occurrence of a pseudo contour even if camera shake occurs, a portable phone, a portable game machine, an electronic book, a video camera, a digital still camera, or the like that is used by being supported by a hand. It is most suitable for use as a display unit included in electronic equipment. In addition, since the semiconductor display device of the present invention can prevent false contours, the semiconductor display device is optimal for an electronic apparatus having a display unit for viewing a video, which can reproduce a moving image such as a display device.

  Other electronic devices that can use the semiconductor display device of the present invention include a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, an audio playback device (car audio, audio component, etc.), and a notebook type personal computer. Examples thereof include a computer, a game machine, and an image playback device (typically, a device having a display that can play back a recording medium such as a DVD: Digital Versatile Disc and display the image). Specific examples of these electronic devices are shown in FIGS.

  FIG. 12A illustrates a mobile phone, which includes a main body 2101, a display portion 2102, a voice input portion 2103, a voice output portion 2104, and operation keys 2105. By manufacturing the display portion 2102 using the semiconductor display device of the present invention, a cellular phone which is one of the electronic devices of the present invention can be completed.

  FIG. 12B illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and an eyepiece. Part 2610 and the like. By manufacturing the display portion 2602 using the semiconductor display device of the present invention, a video camera which is one of the electronic devices of the present invention can be completed.

  FIG. 12C illustrates a display device, which includes a housing 2401, a display portion 2402, a speaker portion 2403, and the like. By manufacturing the display portion 2402 using the semiconductor display device of the present invention, a display device which is one of the electronic devices of the present invention can be completed. The display device includes all information display devices for personal computers, TV broadcast reception, advertisement display, and the like.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields. This embodiment can be freely combined with the above embodiment modes and embodiments.

A pattern used for display in an experiment conducted to examine the relationship between the sharing rate and the occurrence of pseudo contours. When the ratio of the subframe periods SF ₁ was _R 1 (%) in one frame _period, a graph showing _R 1 and (%), the relationship between the minimum frame frequency F which generation of a pseudo contour is observed (Hz). The graph which shows the relationship between frame frequency (Hz) and the minimum share rate (%) which will be able to suppress generation | occurrence | production of a pseudo contour. The graph which shows the relationship between the sub-frame period in the light emission state and the gradation, and the sharing rate R _sh (%) when compared with the case where the gradation is one step lower. 1 is a block diagram illustrating a configuration of a light emitting device of the present invention. FIG. 14 illustrates an example of a pixel included in a light-emitting device of the present invention. 4 is a timing chart when displaying 4-bit gradation in the driving method of the present invention. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 4 is a cross-sectional view of a pixel included in a light-emitting device of the present invention. FIG. 2A and 2B are a top view and a cross-sectional view of a light-emitting device of the present invention. FIG. 14 is a diagram of an electronic device using the light-emitting device of the present invention. The graph which shows the relationship between a gradation ratio and the minimum frame frequency F (Hz) by which generation | occurrence | production of a pseudo contour is recognized. The figure which compared the structure of the conventional sub-frame period, and the structure of the sub-frame period of this application. The graph which shows the relationship between the sub-frame period in the light emission state and the gradation, and the sharing rate R _sh (%) when compared with the case where the gradation is one step lower.

Explanation of symbols

101 Panel 102 Controller 103 Table 104 Pixel Unit 105 Signal Line Driver Circuit 106 Scan Line Driver Circuit 110 Shift Register 111 Latch A
112 Latch B
113 Shift register 114 Buffer

Claims (8)

A table storing data defining the relationship between the gradation of the video signal and the subframe period in which light is emitted among the plurality of subframe periods;
A controller for converting and outputting the video signal according to the data;
A panel in which gradation of pixels is controlled in accordance with the output video signal,
For each gray level of gray level 2 or higher, the number and length of the plurality of subframe periods are determined according to the subframe rate R _SF ,
The sub-frame rate R _SF is calculated according to a sharing rate R _sh determined by a frame frequency. A table storing data defining the relationship between the gradation of the video signal and the subframe period in which light is emitted among the plurality of subframe periods;
A controller for converting and outputting the video signal according to the data;
A panel in which gradation of pixels is controlled in accordance with the output video signal,
For each gray level of gray level 2 or higher, the number and length of the plurality of subframe periods are determined according to the subframe rate R _SF ,
The semiconductor display device, wherein the subframe rate R _SF and the sharing rate R _sh determined by the frame frequency satisfy R _SF = (1−R _sh ) / (2−R _sh ). A table storing data defining the relationship between the gradation of the video signal and the subframe period in which light is emitted among the plurality of subframe periods;
A controller for converting and outputting the video signal according to the data;
A panel in which gradation of pixels is controlled in accordance with the output video signal,
The number and the length of the plurality of subframe periods are determined according to the subframe rate R _SF in each of the intermediate gradation and the highest gradation among the total number of gradations divided into three. ,
The sub-frame rate R _SF is calculated according to a sharing rate R _sh determined by a frame frequency. A table storing data defining the relationship between the gradation of the video signal and the subframe period in which light is emitted among the plurality of subframe periods;
A controller for converting and outputting the video signal according to the data;
A panel in which gradation of pixels is controlled in accordance with the output video signal,
The number and the length of the plurality of subframe periods are determined according to the subframe rate R _SF in each of the intermediate gradation and the highest gradation among the total number of gradations divided into three. ,
The semiconductor display device, wherein the subframe rate R _SF and the sharing rate R _sh determined by the frame frequency satisfy R _SF = (1−R _sh ) / (2−R _sh ). Drive so that a plurality of subframe periods are included in one frame period,
The subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency, and the number and length of the plurality of subframe periods in each gray level of 2 or higher so as to satisfy the sub frame rate R _SF. And a subframe period in which light is emitted among the plurality of subframe periods is defined. Drive so that a plurality of subframe periods are included in one frame period,
The subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency, and the number and length of the plurality of subframe periods in each gray level of 2 or higher so as to satisfy the sub frame rate R _SF. And a sub-frame period in which light is emitted among the plurality of sub-frame periods is defined,
The driving method of the semiconductor display device, wherein the subframe rate R _SF and the sharing rate R _sh determined by the frame frequency satisfy R _SF = (1−R _sh ) / (2−R _sh ) . Drive so that a plurality of subframe periods are included in one frame period,
The subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency, and among the total number of gradations divided in three, each gradation of the intermediate gradation and the highest gradation is the above-mentioned gradation. so as to satisfy the sub-frame rate R _SF, semiconductor, characterized in that the number and length of the plurality of sub-frame periods, and the sub-frame period in which the state of light emission of the plurality of sub-frame periods are defined A driving method of a display device. Drive so that a plurality of subframe periods are included in one frame period,
The subframe rate R _SF is calculated according to the sharing rate R _sh determined by the frame frequency, and among the total number of gradations divided in three, each gradation of the intermediate gradation and the highest gradation is the above-mentioned gradation. In order to satisfy the subframe rate R _SF , the number and length of the plurality of subframe periods and a subframe period in which light is emitted among the plurality of subframe periods are determined,
The driving method of the semiconductor display device, wherein the subframe rate R _SF and the sharing rate R _sh determined by the frame frequency satisfy R _SF = (1−R _sh ) / (2−R _sh ) .

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