JP2004199033A - Display device and its driving method, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which is suitable to a mobile terminal etc., and capable of top/reverse two-surface display and has small module volume. <P>SOLUTION: First and second light-blocking liquid crystal displays are provided so that the top and reverse sides of a light emitting device provided with a plurality of pixels having light emitting elements is sandwiched, and at least one of the devices is formed on the same transparent substrate with the light emitting device. The first and second light-blocking liquid crystal devices have two modes which are a transmission mode and a light blocking mode respectively and when one is in the transmission mode, the other is in the light blocking mode. The light emitting device is a both-surface light emission type to display pictures according to a video signal, and the first and second light-blocking liquid crystal display devices enters the transmission mode and light blocking mode by turns to display pictures independently on the top and reverse surfaces. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a display device provided with a light-emitting element, and particularly to a display device used for a portable information terminal such as a mobile phone and a PDA.

  In recent years, as a light emitting device, research and development of a display device using a self light emitting element typified by an electroluminescence (EL) element or the like instead of a liquid crystal display (LCD) having pixels using a liquid crystal element has been promoted. These light-emitting devices are expected to be widely used as display screens and display devices for mobile phones, taking advantage of the advantages of high image quality due to the self-luminous type, wide viewing angle, and thinness and light weight due to no need of a backlight. ing.

Further, in mobile phones and the like, high added value is required due to diversification of the purpose of use, and recently, a type provided with a sub display surface separately from a normal display surface has been provided (Patent Document 1, Patent Document 2).
JP 2001-86205 A JP 2001-285445 A

  However, in a mobile phone or the like having a sub display surface in addition to the main display surface, in addition to the volume occupied by a module including a backlight and the like, the volume occupied by a substrate or the like on which a control IC or the like for driving them is mounted cannot be ignored. In reality, the sub display surface is limited to a display region much smaller than the main display surface. In particular, recently provided mobile phones and the like are significantly reduced in size and weight, and have a trade-off with higher added value.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a display device capable of displaying a high-definition, large-screen display on both surfaces and having a small volume and modularization.

  In order to solve the above-described problems, the present invention has taken the following measures.

  Conventionally, in a mobile phone or the like, the main display surface and the sub display surface are mounted using independent display devices, respectively, so that there is a problem that the module volume is large. In the present invention, a light-emitting element of a self-luminous type is used as a pixel portion of a display device, and both surfaces of one display device are used as display surfaces, and different images can be displayed on both sides. That is, since one set of drive circuits is required for displaying images on the two display surfaces, one set of external display controller for driving them may be used. Therefore, a high-performance display device that realizes downsizing of the module is provided.

  The configuration of the present invention is described below.

The display device of the present invention
A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a transparent substrate having an insulating surface,
The first and second light-shielding liquid crystal devices are provided on the front and back of the light-emitting device.

The display device of the present invention
A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a transparent substrate having an insulating surface,
The first and second light-blocking liquid crystal devices are provided on the front and back of the light-emitting device, and at least one of them is formed on the same transparent substrate as the light-emitting device.

The display device of the present invention
The light-shielding liquid crystal device formed on the same transparent substrate as the light emitting device is laminated on the surface on which the light emitting device is formed.

The display device of the present invention
A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a first surface on a first transparent substrate having an insulating surface,
One of the first and second light-blocking liquid crystal devices is formed between the first surface of the first transparent substrate and a second transparent substrate having an insulating surface, and the other is: It is characterized in that the first transparent substrate is formed between a back surface of the first surface and a third transparent substrate having an insulating surface.

The display device of the present invention
A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a first surface on a first transparent substrate having an insulating surface,
One of the first and second light-blocking liquid crystal devices is formed between the first surface of the first transparent substrate and a second transparent substrate having an insulating surface, and the other is: It is formed between third and fourth transparent substrates having an insulating surface, and is bonded to the back surface of the first surface of the first transparent substrate.

The driving method of the display device of the present invention,
In a display device including a light-emitting device provided with a plurality of pixels having light-emitting elements and first and second light-blocking liquid crystal devices,
The first and second light-blocking liquid crystal devices are provided on the front and back of the light emitting device, respectively.
The light emitting device displays an image according to an image signal,
The first and second liquid crystal devices for light shielding are characterized by taking two modes, a transmission mode and a light shielding mode, respectively.

The driving method of the display device of the present invention,
In a display device including a light-emitting device provided with a plurality of pixels having light-emitting elements and first and second light-blocking liquid crystal devices,
The first and second light-blocking liquid crystal devices are provided on the front and back of the light emitting device, respectively.
The light emitting device displays an image according to an image signal,
The method of driving a display device, wherein the first and second liquid crystal devices for light shielding take three modes: a transmission mode, a semi-transmission mode, and a light shielding mode, respectively.

In the present invention,
The first and second light-blocking liquid crystal devices include:
When one is in the transmission mode, the other is in the light shielding mode.

In the present invention,
The switching between the light-shielding mode and the transmission mode of the first and second light-shielding liquid crystal devices is performed in synchronization with a frame period in which the light-emitting device displays an image.

In the present invention,
The switching between the light-shielding mode and the transmission mode of the first and second light-shielding liquid crystal devices is performed at an arbitrary timing by a user operation.

  According to the present invention, a large-screen, high-definition display can be obtained on both the main display surface and the sub-display surface, and a display device with a small module volume is realized. In addition, since black display appears periodically through the display of each surface, afterimages in moving image display are reduced, and motion of the image is recognized more sharply.

  One embodiment of the present invention is shown in FIG. In FIG. 1A, a module surrounded by a dotted frame 101 includes a display device 102 and a display controller 103. As illustrated in FIG. 1B, the display device 102 includes a light-emitting device 110 and first and second light-blocking liquid crystal devices 121 and 122 provided so as to sandwich the light-emitting device 110.

  FIG. 2A illustrates the light-emitting device 110 in detail. A pixel portion 201, a source signal line driver circuit 202, and a gate signal line driver circuit 203 are provided over a substrate 200. Control signals for each driver circuit and current supply to the pixel portion 201 are supplied to a flexible printed circuit (FPC) 204 Done by In the pixel portion, a plurality of pixels are arranged in a matrix, and a portion surrounded by a dotted frame 210 corresponds to one pixel.

  FIG. 2B illustrates a structural example of a pixel. It includes a source signal line 211, a gate signal line 212, a current supply line 213, a switching TFT 214, a driving TFT 215, a storage capacitor 217, a light emitting element 216, and a counter electrode 218.

  As shown in FIG. 1B, each of the first and second light-blocking liquid crystal devices 121 and 122 has a pair of pixel electrodes having a shape and an area capable of covering the entire pixel portion 120 of the light-emitting device 110. It has a liquid crystal element 125 sandwiched between 123 and 124, and takes two states of a transmission mode or a light-shielding mode over the entire surface according to a voltage applied to the pixel electrodes 123 and 124. Although not particularly shown in FIG. 1B, a polarizing plate may be provided outside the pixel electrodes 123 and 124. However, the place where the polarizing plate is provided is not limited to this.

  In the display device 102, a surface on which the first light-blocking liquid crystal device 121 is provided is referred to as a first display surface, and a surface on which the second light-blocking liquid crystal device 122 is provided is referred to as a second display surface.

  The operation will be described. Generally, in a display such as a CRT (Cathode Ray Tube: cathode tube) type used for a personal computer or a display device such as an LCD (liquid crystal display), the screen is rewritten about 60 times per second. . This is required so that the viewer does not perceive the flicker of the screen without recognizing the rewriting operation. In the present invention, this rewriting is doubled. Although the number of times is not particularly limited, assuming that 60 times per second is a standard example, 120 rewrites are performed per second. The first and second light-blocking liquid crystal devices 121 and 122 are driven in synchronization with the rewriting cycle.

  The situation at this time is shown in FIG. As an example, an example in which 120 frames are made per second is shown. In synchronization with the switching of the frame period, the driving signals of the light-shielding liquid crystal devices 121 and 122 repeat H level and L level. According to this timing, the first and second light-blocking liquid crystal devices 121 and 122 switch between the transmission mode and the light-blocking mode, respectively. In the first, third, fifth,..., And 119th frames, the first light-shielding liquid crystal device 121 is in the transmission mode, and the second light-shielding liquid crystal device 122 is in the light-shielding mode. In the second, fourth, sixth,..., And 120th frames, the first light-shielding liquid crystal device 121 is in the light-shielding mode, and the second light-shielding liquid crystal device 122 is in the transmission mode. That is, an image that appears through the first light-blocking liquid crystal device 121 is visually recognized on the first display surface through the first, third, fifth,..., 119 frames (total of 60 frames). The image appearing through the second light-blocking liquid crystal device 122 is visually recognized on the second display surface through the second, fourth, sixth,..., 120th frames (total of 60 frames). Become.

  Subsequently, an operation in one frame period will be described.

  One frame period includes an address (write) period 301 and a sustain (light emission) period 302 as shown in FIG. A non-display period 303 is provided before and after both.

  In the address (write) period 301, a row selection pulse is sequentially output from the first row by the gate signal line driving circuit, and in the selected row, a pixel of the video signal output to the source signal line is supplied to the pixel. Write. At this time, no current is supplied to the light emitting elements over the entire row. For example, in FIG. 2B, the current supply line 213 and the counter electrode 218 have substantially the same potential (if there is a potential difference, the potential difference is kept at a level not exceeding the threshold voltage of the light emitting element). Method.

  When the gate signal line in the last row is selected and the writing of the video signal to the pixel in the last row is completed, the process proceeds to a sustain (light emission) period 302. By giving a potential difference between the current supply line 213 and the counter electrode 218 which have the same potential in the address (write) period 301, a current flows through the light emitting element 216, and light emission continues until the frame period ends. Thereafter, the non-display period 303 starts again.

  The above operation is performed in each frame period to display an image. By the way, on the first and second display surfaces, during the frame period during which video is displayed on one side, the other is shielded from light, which is equivalent to performing black display. In this way, by performing the display such as video display → black display → video display → black display..., The afterimage in the moving image display is reduced, and the motion of the video is recognized more sharply.

  For driving the light-shielding liquid crystal devices 121 and 122, an independent driving signal corresponding to a frame frequency of 120 Hz may be used, or a driving signal may be generated from a signal used in the display device 102. good.

  In this embodiment, a structure of a driving circuit for driving a display device formed by using the present invention will be described.

  FIG. 4 shows a configuration example of a source signal line driver circuit for performing display mainly using an analog video signal as a video signal.

  The example in FIG. 4A includes a shift register 402 using a plurality of flip-flops 401, a NAND 403, a level shifter 404, a buffer 405, and a sampling switch 406.

  The operation will be described. The shift register 402 sequentially outputs sampling pulses according to the clock signals (S-CK, S-CKb) and the start pulse (S-SP). In some cases, two consecutive sampling pulses have a period in which the pulses overlap each other. In such a case, the NAND 403 performs an operation with the preceding and succeeding sampling pulses. Depending on the configuration of the shift register 402, the NAND 403 may not be needed.

The sampling pulse output from the NAND 403 undergoes amplitude conversion by the level shifter 404 if necessary, is amplified by the buffer 405, and is input to the sampling switch 406. In the sampling switch 406, captures the analog video signal (Video), which is inputted in the input timing of the sampling pulse is output at point sequentially each of the source signal line S ₁ to S _n.

  Here, the level shifter 404 and the buffer 405 are not particularly required if the shift register 402 or the NAND 403 itself has sufficient ability to drive a large load.

  FIG. 4B has a basic configuration similar to that of FIG. 4A, except that the buffer 405 drives a plurality of sampling switches 406 per stage. With such a configuration, the video signal can be captured in a plurality of columns at the same time as one sampling pulse is output. Therefore, as compared with the configuration in FIG. Operating frequency can be lowered. In general, driving in which k video signals are simultaneously captured by one sampling pulse is called k-division driving. If the number of source signal lines is the same, the configuration shown in FIG. , 1 / k. However, since k video signals are taken in at the same time, k video signals need to be input in parallel.

  FIG. 5 shows a configuration example of a source signal line driver circuit for performing display mainly using a digital video signal as a video signal.

  The example in FIG. 5A includes a shift register 502 including a plurality of flip-flops 501, a NAND 503, a first latch circuit 504, a second latch circuit 505, and a D / A conversion circuit 506.

  The operation will be described. However, the operations of the shift register to the NAND are the same as those shown in FIG.

  In accordance with the timing at which the sampling pulse is input, the first latch circuit 504 captures a digital video signal (Data). Here, the three first latch circuits 504 in parallel take in digital video signals for three bits at the same time. The captured digital video signal is held in each of the first latch circuits 504.

  The above operations are performed sequentially from the first column. When the latch signal (LAT) is input after the capture of the digital video signal in the first latch circuit 504 in the last column is completed, the digital video signals held in the first latch circuit 504 are simultaneously transferred to the first latch circuit 504. 2 to the second latch circuit 505. Thereafter, the digital video signals for one row are processed in parallel.

Digital image signal transferred to the second latch circuit 505 is subsequently input to the D / A conversion circuit 506 receives the D / A converter, converted into an analog voltage signal, a source signal line S ₁ to S Output to _n .

  The example of FIG. 5B illustrates a configuration in the case of performing display by a digital time gray scale method. One first latch circuit 504 and one second latch circuit 505 are arranged per column, and a digital video signal (Data) is input in series from one signal line. As an example, the first column first bit data → the second column first bit data →... → the last column first bit data → the first column second bit data → the second column second bit data →. → The second bit data of the last column → ・ ・ ・ → Least bit data of the first column → Least bit data of the second column → ・ ・ ・ → Least bit data of the last column . The operation of each unit is the same as that in FIG. 5A, and a description thereof will not be repeated.

  FIG. 6 shows a configuration example of the gate signal line driving circuit.

  The example in FIG. 6 includes a shift register 602 using a plurality of flip-flops 601, a NAND 603 level shifter 604, and a buffer 605, similarly to the source signal line driver circuit. Here, as in the case of the source signal line driver circuit, the NAND 602, the level shifter 603, and the buffer 604 may be provided as needed.

As in the operation of the source signal line driving circuit, the row selection pulse is sequentially output from the shift register 602, an operation is performed between adjacent pulses in the NAND 603, the amplitude is converted in the level shifter 604, and the buffer 605 is operated. Via the gate signal lines G _{1 to} G _m , and are sequentially selected from the first row. The gate signal line driving circuit may be used in combination with any of the aforementioned source signal line driving circuits.

  In this embodiment, a configuration including a display controller for controlling a display device will be described.

  FIG. 7 schematically shows a display device and a display controller. Signals and power for driving the light-emitting device 702 and the first and second light-blocking liquid crystal devices 703 and 704 included in the display device 701 are supplied by the display controller 730. Specifically, a source side clock signal (SCK), a source side start pulse (SSP), a latch signal (LAT), a gate side clock signal (GCK), a gate side start pulse (GSP), a power supply for a driving circuit, a light emitting element Power supply is supplied.

  The signal control circuit 720 includes a CPU 721, a memory controller 722, a memory A 723, and a memory B 724. The video signal (Data) is read by the memory controller 722 controlling writing and reading of the memory A 723 and the memory B 724. The data is input to the display device 701.

  Here, the operation of writing and reading the video signal to and from the memory according to the present invention will be described.

  In the present invention, as shown in FIG. 8, a video signal 801 for the first display surface and a video signal 802 for the second display surface are sequentially input to the signal control circuit 720 from outside. Here, FIG. 8 shows the video signals 801 and 802 for 60 frames.

  The memory controller 722 controls writing and reading of each of the memory A 723 and the memory B 724. The video signal 801 is stored in the memory A 723, and the video signal 802 is stored in the memory B 724. Here, the memory A 723 and the memory B 724 need a storage capacity that can store at least one frame of video signal. Note that video signals for a plurality of frames may be stored and read out by switching every frame period.

  After the storage of the video signals in both memories is completed, the memory controller 722 alternately controls reading of the memories A 723 and B 724 and outputs the video signals 801 and 802 alternately for each frame. The video signal 803 output in such an order is input to the display device 701 and displayed on each of the first and second display surfaces (see FIG. 3).

  Subsequently, details of the display controller 730 and the memory controller 722 will be described.

  The display controller 730 supplies a clock signal and a start pulse to the source signal line driver circuit 705 and the gate signal line driver circuit 706 of the display device 701 as shown in FIG. In addition, it also has a role as a power supply to each drive circuit and the light emitting element.

  As shown in FIG. 9A, the display controller 730 includes a frequency dividing circuit 901, a horizontal clock generating circuit 902, a vertical clock generating circuit 903, a power control circuit 904, and the like.

  Signals input from the CPU to the display controller 730 include a reference clock signal 911, a horizontal synchronization signal 912, a vertical synchronization signal 913, and the like. A clock signal having a desired frequency is generated from the reference clock signal 911 by the frequency dividing circuit 901 and input to the horizontal clock generating circuit 902 and the vertical clock generating circuit 903.

  The horizontal synchronization signal 912 is input to a horizontal clock generation circuit 902, and the horizontal clock generation circuit 902 generates a source clock signal (SCK) and a source start pulse (SSP) based on the input signals.

  The vertical synchronization signal 913 is input to the vertical clock generation circuit 903, and the vertical clock generation circuit 903 generates a gate clock signal (GCK) and a gate start pulse (GSP) based on the input signals. Further, here, a liquid crystal device driving signal for light shielding (LCD Ctrl.) Is generated based on the vertical synchronization signal 913.

  The power supply control circuit 904 is supplied with a reference power supply 914, and generates a power supply for a source signal line drive circuit, a power supply for a gate signal line drive circuit, a power supply for driving a light emitting element, and the like.

  As shown in FIG. 9B, the memory controller 722 includes a frequency dividing circuit 921, a memory R / W control circuit 922, X counters 923 and 925, Y counters 924 and 926, X decoders 927 and 929, and a Y decoder 928. 930 and the like.

  Signals input from the CPU to the memory controller 722 include a reference clock signal 911, a vertical synchronization signal 913, and the like. A clock signal having a desired frequency is generated by the frequency dividing circuit 921 from the reference clock 911, and the X counters 923 and 925 and the Y counters 924 and 926 are controlled. X address and Y address are selected. In accordance with this, writing and reading of a video signal are performed for a desired address of each memory.

  In addition, the memory R / W control circuit 922 selects a memory from which a video signal is read for each frame period according to the vertical synchronization signal 913.

  Here, since the light-shielding liquid crystal device drive signal (LCD Ctrl.) And the memory R / W control signal are switched based on the frame period, the timing is controlled using the vertical synchronization signal. There is no limitation to this method. Alternatively, a gate-side start pulse may be used, or a control signal independent from the outside may be input.

  A cross-sectional configuration of the display device of the present invention will be described.

  FIG. 13A is a cross-sectional view. A base film 5002 is formed over a substrate 5001, and TFTs 5003 to 5005 are formed thereon. Here, the TFTs 5003 and 5004 are an N-type TFT and a P-type TFT, respectively, and a pair constitutes a CMOS. The TFT 5005 corresponds to a driving TFT that controls current supply to a light-emitting element. Note that reference numeral 5006 denotes a gate insulating film. Here, the gate insulating film is also formed in the region where the TFT is not formed, but the region where the TFT is not formed may be removed at the time of patterning.

  A first interlayer insulating film 5007 and a planarizing film 5008 are formed so as to cover the TFTs 5003 to 5005. In the case where the first interlayer insulating film 5007 has a sufficient thickness and is made of a material having excellent flatness, the flattening film 5008 is not particularly necessary. A contact hole is opened at a desired position on the flattened surface, and a wiring 5009 is formed.

  Next, a pixel electrode 5010 is formed so as to be in contact with the drain wiring of the TFT 5005. Since the pixel electrode 5010 is required to have a light-transmitting property, the pixel electrode 5010 is preferably formed using a transparent conductive material such as ITO.

  After the formation of the pixel electrode 5010, an edge cover film 5011 serving as a partition of a light-emitting element is formed, and a portion serving as a light-emitting region is opened, and a light-emitting layer 5012 is formed. Examples of a method for forming the light-emitting layer 5012 include, but are not particularly limited to, various methods such as a method using vapor deposition and a method using coating by an inkjet method.

  A counter electrode 5013 is formed so as to cover the light-emitting layer 5012. Since the opposing electrode 5013 is also required to have a light-transmitting property, it is preferable to use a transparent conductive material.

  Incidentally, one of the pixel electrode 5010 and the counter electrode 5013 serves as an anode of the light emitting element and the other serves as a cathode. In general, it is considered desirable that the anode be made of a material having a high work function and excellent in hole emission, and the cathode be made of a material having a low work function and excellent electron emission. In this case, there is a method of forming the cathode with a very thin metal film as a method of achieving both the light transmission property and the electron emission property on the cathode side. According to such a method, since the film thickness is extremely small, light emitted from the light-emitting layer 5012 passes through the film and appears to the outside. Further, the wiring resistance may be reduced by forming a transparent conductive material by laminating with a metal film and giving the transparent conductive material a thickness.

  After formation of the counter electrode 5013, a barrier layer 5014 or the like may be provided to prevent entry of moisture or the like into the light-emitting layer 5012. Through the above steps, the light-emitting device 5100 is completed.

  Subsequently, a second planarization film 5015 is formed over the barrier layer 5014, and a liquid crystal pixel electrode 5016 is formed over the planarized surface. Since the light-blocking liquid crystal device only needs to take a transmission mode and a light-blocking mode over the entire display section, the liquid crystal pixel electrode 5016 may be formed uniformly over the entire display section.

  Next, a substrate 5020 is prepared. A liquid crystal pixel electrode 5019 is formed over a substrate 5020. Thereafter, the two are bonded via a spacer 5017 so as to face the pixel electrode for liquid crystal 5016. After that, a liquid crystal material 5018 is injected into the void portion, and the injection port is sealed, whereby the first liquid crystal device for light shielding 5200 is completed.

On the other hand, a liquid crystal pixel electrode 5021 is formed on the back surface of the substrate 5001 on which the above-described element group is formed. It may be formed directly on the substrate 5001 or, although not shown, may be formed on another substrate first and then transferred.

  As in the case of the first light-blocking liquid crystal device 5200, a substrate 5025 is prepared. A liquid crystal pixel electrode 5024 is formed over a substrate 5025. Thereafter, the two are bonded together via a spacer 5022 so as to face the liquid crystal pixel electrode 5021. After that, the liquid crystal material 5023 is injected into the gap, and the injection port is sealed, whereby the second light-shielding liquid crystal device 5300 is completed. Through the above steps, the entire display device is completed.

  Note that the second light-blocking liquid crystal device 5300 may be formed independently using substrates 5025 and 5050 as shown in FIG. Further, the first light-blocking liquid crystal device 5200 may be formed independently on a substrate different from the light-emitting device 5100. Note that in order to reduce the thickness of the entire display device, at least one of the first light-blocking liquid crystal device 5200 and the second light-blocking liquid crystal device 5300 is stacked over the light-emitting device 5100 as described above. Although it is desirable to form the device, a manufacturing method may be appropriately selected in consideration of the size and the like of a device manufactured using the display device.

  FIG. 11 shows an example of a mobile phone capable of performing main display and sub-display using a conventional display device, and FIG. 12 shows an example of performing main display and sub-display using the display device of the present invention. Here is an example of a mobile phone that can be used. In addition, in order to be able to express the difference between the two, the common parts are shown as completely the same configuration.

  The mobile phone illustrated in FIG. 11 includes a first housing 1101 and a second housing 1108, and has a shape that can be folded. A first display device (for main display) 1102 and a second display device (for sub display) 1103 are built in the first housing 1101, and the respective display devices are controlled by display controllers 1104 and 1105. ing. Further, a speaker 1106 and an antenna 1107 are provided in the first housing 1101.

  In the second housing 1108, a main body driving module 1109, an operation button module 1110, a microphone 1112, and a battery 1113 are incorporated. The first housing 1101 and the second housing 1108 are connected to each other via a hinge 1111.

  At this time, the first display area is indicated by 1151 and the second display area is indicated by 1152. In addition, the thickness of the housing on which the display device is provided, that is, the thickness of the first housing 1101, is indicated by T1.

  The mobile phone illustrated in FIG. 12 includes a first housing 1131 and a second housing 1108. The configuration on the second housing 1108 side is the same as that of the conventional example shown in FIG. The display device 1132 of the present invention is controlled by only one display controller 1133. The first display area is indicated by 1161, and the second display area is indicated by 1162. The thickness of the housing on which the display device is provided, that is, the thickness of the first housing 1131 is indicated by T2.

  Comparing the sizes of the second display area in both cases, it can be said that the case where the display device of the present invention is used is far more suitable for increasing the screen size. Further, the thickness of the first housing is much longer in T2 when the display device of the present invention is used than in the conventional T1 in which the main display and the sub-display are provided by two independent display devices. It can be seen that the thickness can be reduced.

  As described above, the display device of the present invention can greatly contribute to miniaturization and high functionality of portable information terminals such as portable telephones.

  In the first and second embodiments, the configuration and the method for simultaneously and independently displaying an image on the first and second display surfaces have been described. This is intended for a case where a plurality of people look at the screen from both sides with the portable information terminal having the shape shown in the fourth embodiment in between. On the other hand, it is unlikely that a single user uses both sides at the same time in a mobile phone or the like having a large percentage of personal uses.

  For example, in applications such as e-mail transmission / reception, if a user displays an image using only the first display surface, the second display surface does not need to display an image. Rather, from the viewpoint of privacy protection, it may be desirable that when the user is looking at one display surface, nothing is displayed on the other display surface.

  In such a case, in FIG. 1B, the first light-shielding liquid crystal device 121 is always set to the transmission mode, and the second light-shielding liquid crystal device 122 is always set to the light-shielding mode. In this case, a signal may be input so that an image is displayed only on the first display surface. In the same manner, it is also possible to display an image only on the second display surface and not display anything on the first display surface.

  In the case of a foldable portable information terminal such as the one shown in FIG. 1A, the inner display surface is invisible when the rear display surface is used with the housing closed. Therefore, the mode switching of the light-shielding liquid crystal device is not particularly limited here. However, in the transmissive mode, there is a possibility that light passes through the other side of the display surface depending on the transmittance of the display device 102. Therefore, the light-shielding liquid crystal device on the inner display surface should be in the light-shielding mode. preferable.

  According to the above method, the display device of the present invention can be easily replaced with the display device of the present invention for the completely same application as the portable information terminal using the conventional display device.

  In this case, since only the first display surface is displayed during the entire display period, it is not particularly necessary to set the frame frequency to 120 Hz as described in the preferred embodiment.

  In the display device of the present invention, the first and second light-blocking liquid crystal devices provided on the front and back of the light-emitting device correspond to the best mode for carrying out the invention, and in other embodiments, correspond to the image to be displayed, the use form, and the like. Preferably, the transmission mode and the light-shielding mode are automatically selected respectively, but the user may be able to freely set the transmission mode and the light-shielding mode.

  In the first and second light-shielding liquid crystal devices, the transmission mode and the light-shielding mode are controlled by applying a potential difference between a pair of electrodes sandwiching a liquid crystal element, as in the conventional liquid crystal display device. I have. Therefore, by controlling the voltage applied between the pair of electrodes, it is easy to set the transmissive mode, the light blocking mode, the semi-transmissive mode, and the like. Such a mode can be used, for example, for adjusting the contrast of the screen. Of course, the application is not limited to this.

  The display device of the present invention has various uses. In this embodiment, examples of electronic devices to which the present invention can be applied will be described.

  FIG. 10A illustrates a mobile phone, which includes a housing 1000, a first display surface 1001, operation buttons 1002 and 1004, a second display surface 1003, a lens 1005, and the like. The display device of the present invention can be used for the first display surface 1001 and the second display surface 1002. Since a single display device can perform display in two directions on the front and back of the substrate, the thickness of the housing 1000 can be reduced even when display portions are provided on both surfaces as shown in FIG. It becomes possible.

  As an example of use, when the terminal is opened, the first display surface 1001 is mainly used as a display surface. The screen operation at this time is performed using the operation button 1002. Conventionally, the second display surface 1002 mainly used in a state in which the terminal is closed could only be built in a small size due to space limitations. However, according to the present invention, the second display surface 1002 is equivalent to the first display surface 1001. Using the second display surface 1002 having the display size, browsing of a mail, a Web page, and the like becomes possible. The operation in the closed state is performed by the operation button 1004.

  In recent years, mobile phones equipped with a digital camera have become widespread. Even when shooting with the lens 1005 facing forward, shooting can be performed while monitoring on the second display surface 1002 having a wide display area. It becomes.

  FIG. 10B illustrates a personal computer, which includes a housing 1011, a pointing device 1012, a display portion 1013, a keyboard 1014, and the like. The display device of the present invention can be used for the display portion 1013. In such a case, the tablet can be used as a tablet computer with the display unit closed.

  FIG. 10C illustrates a portable information terminal, which includes a main body 1021, a stylus 1022, a display portion 1023, operation buttons 1024, an external interface 1025, and the like. The display device of the present invention can be used for the display portion 1023.

  As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electronic devices in all fields. Further, the electronic apparatus of this embodiment may be applied in combination with any of the configurations shown in the first to fourth embodiments.

The figure which shows one Embodiment of this invention. FIG. 2 is a diagram illustrating a structure of a general display device using a light-emitting element in a pixel portion. FIG. 5 is a diagram illustrating display timing in the display device of the present invention. FIG. 4 illustrates a configuration example of a source signal line driver circuit. FIG. 4 illustrates a configuration example of a source signal line driver circuit. FIG. 4 illustrates a configuration example of a gate signal line driver circuit. FIG. 3 is a diagram illustrating a configuration example of a module including a display controller. The figure which shows the outline of the reading and writing of a video signal. FIG. 3 is a diagram illustrating a configuration example of a display controller and a memory controller. FIG. 13 illustrates an example of an electronic device to which the present invention can be applied. FIG. 4 is a cross-sectional view of a conventional mobile phone. FIG. 9 is a cross-sectional view when the present invention is applied to a mobile phone. FIG. 2 is a diagram illustrating a cross-sectional configuration of a display device of the present invention.

Claims (11)

A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a transparent substrate having an insulating surface,
The display device, wherein the first and second light-blocking liquid crystal devices are provided on the front and back of the light-emitting device. A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a transparent substrate having an insulating surface,
The display device, wherein the first and second light-blocking liquid crystal devices are provided on the front and back of the light emitting device, and at least one of them is formed on the same transparent substrate as the light emitting device. In claim 2,
A display device, wherein a light-shielding liquid crystal device formed on the same transparent substrate as the light emitting device is laminated on a surface on which the light emitting device is formed. A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a first surface on a first transparent substrate having an insulating surface,
One of the first and second light-blocking liquid crystal devices is formed between the first surface of the first transparent substrate and a second transparent substrate having an insulating surface, and the other is: The display device, wherein the first transparent substrate is formed between a back surface of the first surface and a third transparent substrate having an insulating surface. A light-emitting device provided with a plurality of pixels having light-emitting elements, first and second light-blocking liquid crystal devices,
The light emitting device is formed on a first surface on a first transparent substrate having an insulating surface,
One of the first and second light-blocking liquid crystal devices is formed between the first surface of the first transparent substrate and a second transparent substrate having an insulating surface, and the other is: A display device formed between third and fourth transparent substrates having an insulating surface, and bonded to a back surface of the first surface of the first transparent substrate. In a display device including a light-emitting device provided with a plurality of pixels having light-emitting elements and first and second light-blocking liquid crystal devices,
The first and second light-blocking liquid crystal devices are provided on the front and back of the light emitting device, respectively.
The light emitting device displays an image according to an image signal,
The first and second light-blocking liquid crystal devices take two modes, a transmission mode and a light-blocking mode, respectively. In a display device including a light-emitting device provided with a plurality of pixels having light-emitting elements and first and second light-blocking liquid crystal devices,
The first and second light-blocking liquid crystal devices are provided on the front and back of the light emitting device, respectively.
The light emitting device displays an image according to an image signal,
The method of driving a display device, wherein the first and second liquid crystal devices for light shielding take three modes: a transmission mode, a semi-transmission mode, and a light shielding mode, respectively. In claim 6,
The first and second light-blocking liquid crystal devices include:
A method for driving a display device, wherein one is in a light-transmitting mode and the other is in a light-shielding mode. In claim 6 or claim 8,
The method of driving a display device, wherein switching between the light-shielding mode and the transmission mode of the first and second light-shielding liquid crystal devices is performed in synchronization with a frame period in which the light-emitting device displays an image. In claim 6 or claim 7,
A method of driving a display device, wherein switching between the light-shielding mode and the transmission mode of each of the first and second light-shielding liquid crystal devices is performed at an arbitrary timing by a user operation. An electronic apparatus using the display device according to any one of claims 1 to 5, or the method for driving the display device according to any one of claims 6 to 8.

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