Liquid crystal display device

Abstract

To provide a liquid crystal display device which can display an image in both modes of a reflective mode with external light used as an illumination light source and a transmissive mode using a backlight.SOLUTION: In one pixel, a region (reflection region) where light made incident through a liquid crystal layer is reflected to perform display and a region (transmission region) where light from a backlight is transmitted to perform display are disposed. Therein, image display can be performed in both modes of a reflective mode with external light used as an illumination light source and a transmissive mode with the backlight used as an illumination light source. In addition, two transistors connected to respective different pixel electrode layers are disposed in one pixel and two transistors are separately operated, so that display in the reflection region and display in the transmission region can be independently controlled.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a semiconductor device having a circuit composed of transistors and a method for manufacturing the same. For example it relates to an electronic device equipped with an electro-optical device typified by a liquid crystal display panel as a component.

Background Art

[0002] In a liquid crystal display device, in order to obtain a high-quality image, pixel electrodes are arranged in a matrix form, and an active matrix type liquid crystal display device using a transistor as a switching element connected to each of the pixel electrodes has attracted attention.

[0003] An active matrix type liquid crystal display device using a transistor having a metal oxide as a channel formation region as a switching element connected to each of the pixel electrodes is already known (see Patent Document 1 and Patent Document 2).

[0004] In addition, active matrix type liquid crystal display devices are roughly classified into two types: transmissive type and reflective type.

[0005]

[0006]

[0007] <00,00034>

[0008] ​Furthermore, reflective liquid crystal displays utilize the optical modulation effect of liquid crystals to filter ambient light, i.e., incident light. There are two states: one where the light is reflected by the electrode and output to the outside of the device, and another where the incident light is not output to the outside of the device. By selecting options, displaying light and dark areas, and then combining them, an image is displayed. It is.

[0008] Reflective liquid crystal displays do not use a backlight, unlike transmissive liquid crystal displays. Therefore, it has advantages such as low power consumption, and demand for it as a portable information terminal is increasing. I'm waiting.

[0009] Reflective liquid crystal displays utilize ambient light, making them suitable for displaying images in environments with strong ambient light, such as outdoors. It is suitable for this purpose. On the other hand, in environments where the surroundings of the liquid crystal display are dim, that is, where ambient light is weak, the display may not be recognizable. It is difficult to do. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2007-123861 [Patent Document 2] Japanese Patent Publication No. 2007-96055 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] To provide a liquid crystal display device that can display images even in dimly lit environments. This will be one of the challenges.

[0012] Furthermore, it offers both a reflection mode that uses ambient light as the illumination source and a transmission mode that uses a backlight. One of the objectives is to provide a liquid crystal display device that enables image display.

Means for Solving the Problem

[0013] In one pixel, a region (reflection region) that reflects light incident through a liquid crystal layer to perform display and a region (transmission region) that transmits light from a backlight to perform display are provided, and as an illumination light source images can be displayed in both a reflection mode using external light and a transmission mode using a backlight. Also, two transistors each connected to a different pixel electrode layer are provided in one pixel, and by operating the two transistors separately, the display region of the connected pixel electrode layer can be independently controlled. When there is external light and its brightness is sufficient, this liquid crystal display device operates in the reflection mode, and furthermore, power consumption can be reduced by displaying a still image.

[0014] When the external light is weak or there is no external light at all, the backlight is turned on in the transmission mode to enable image display. <000008​​​​​​​​​​​​​​​​​​​​​​​​​​One aspect of the present invention disclosed herein comprises a display panel, a backlight unit, and an image processing circuit. The display panel has light-transmitting properties and is in contact with the first set of scan lines and the first set of signal lines. A first system of pixel electrodes that controls the alignment state of the liquid crystal is connected to the first system of pixel electrodes. A transistor is provided, a first system of subpixels is provided, and a second system of reflects visible light. A second set of pixel electrodes, connected to the scan line and the second set of signal lines, controls the alignment state of the liquid crystal. A transistor connected to the second system of pixel electrodes, and a second system of sub-pixels provided therein. Multiple pixels including pairs of pixels, and a first drive circuit that temporally controls the pixel section including the multiple pixels. The backlight section is provided with multiple light-emitting elements and a mechanism that controls the multiple light-emitting elements over time. The image processing circuit has two drive circuits, and the image processing circuit has a memory circuit that stores image signals, and stores in the memory circuit It has a comparison circuit that compares the image signals and calculates the difference, and the comparison circuit detects the difference. The image processing circuit determines that a continuous frame period constitutes a video period and processes the first system of the display panel. The first signal, including video, is output to the signal line, and the image processing circuit outputs the first signal to the backlight section. A video mode that outputs a second signal synchronized with the signal, and a comparison circuit that does not detect differences The image processing circuit determines that the consecutive frame period is a still image period and processes the still images of the still image period. The image is converted to a black and white still image, and the image processing circuit sends the black and white still image to the second signal line of the display panel. The first signal containing the signal is output, and the image processing circuit stops outputting the signal to the backlight section. This is a liquid crystal display device that has a still image mode.

[0019] Another aspect of the present invention disclosed herein includes a display panel, a backlight unit, and an image processing unit. It has a circuit and a photometric circuit, and the display panel is translucent, and has a first system of scanning lines and a first system A first system of pixel electrodes is connected to the signal line and controls the alignment state of the liquid crystal, and the first system of pixels A transistor connected to the elementary electrode, a first system of sub-pixels provided with a visible light reflector It is connected to the second scanning line and the second signal line, and controls the alignment state of the liquid crystal. A second system is provided, which includes a pixel electrode system and a transistor connected to a second system of pixel electrodes. Multiple pixels including pairs of subpixels of a system, and a pixel area containing multiple pixels that is controlled in time. A drive circuit is provided, and the backlight section has multiple light-emitting elements, and the multiple light-emitting elements are controlled by time The image processing circuit has a second drive circuit that controls the image signal, and the image processing circuit has a memory circuit that stores the image signal. It has a comparison circuit that compares image signals stored in a memory circuit and calculates the difference, and the comparison circuit, The image processing circuit determines that the consecutive frame period in which differences were detected constitutes a video period, and then displays the video. The first signal containing video is output to the first signal line of the Nell, and the image processing circuit backlash In the video mode, the light section outputs a second signal synchronized with the first signal, and the comparison circuit is... The image processing circuit determines that a period of consecutive frames that are not detected is a still image period and processes the image as a still image. The still image of the period is converted into a black and white still image, and the image processing circuit then processes the second signal line of the display panel. The first signal, which includes a black and white still image, is output to the backlight unit, and the image processing circuit outputs the signal to the backlight unit. It has a still image mode that stops power, and the still image mode is controlled according to the brightness of the ambient light detected by the photometering circuit. This is an LCD display that adjusts the brightness using the backlight when switching between screen and video modes. ru.

[0020] Another aspect of the present invention disclosed herein includes a display panel, a backlight unit, and an image processing unit. The circuit has a display panel that is translucent and has a first set of scan lines and a first set of signal lines. A first system of pixel electrodes is connected to the first system of pixel electrodes and controls the alignment state of the liquid crystal. A transistor containing a continuous oxide semiconductor layer, and a first system of subpixels provided therein, It reflects the light being seen, is connected to the second scanning line and the second signal line, and controls the alignment state of the liquid crystal. A second system of pixel electrodes and an oxide semiconductor layer connected to the second system of pixel electrodes are included. A plurality of pixels including a second system of subpixels provided with a transistor, and a plurality of pixels A first drive circuit is provided to temporally control the included pixel section, and the backlight section has multiple LEDs It has an optical element and a second drive circuit that temporally controls multiple light-emitting elements in the backlight section. The image processing circuit consists of a memory circuit that stores image signals and a comparison circuit that stores image signals in the memory circuit. It has a comparison circuit that calculates the difference, and the comparison circuit detects the difference over a continuous frame period. The image processing circuit determines that this is a video period and includes the video in the first signal line of the display panel. The first signal is output, and the image processing circuit sends a second signal to the backlight section that is synchronized with the first signal. The video mode that outputs the signal and the comparison circuit determine a continuous frame period during which no difference is detected. The image processing circuit determines that it is a still image period and converts the still image data from that period into a black and white still image. The image processing circuit converts the first signal, which contains a black and white still image, to the second signal line of the display panel. The system outputs a signal, and the image processing circuit stops outputting a signal to the backlight section, entering a still image display mode. It is a liquid crystal display device.

[0021] The above configuration solves at least one of the above problems.

[0022] Furthermore, multiple structures are provided for a single pixel, and reflective electrodes are provided on the side surface of the structures, and the upper part of the structure One aspect of this invention is the use of pixel electrodes having transparent electrodes.

[0023] Furthermore, the liquid crystal display device disclosed herein also comprises a solar cell, and the solar cell and display The panel is attached in a way that allows it to be opened and closed, and the power from the solar cell is used to power the display panel, backlight section, and This can provide electronic equipment that supplies power to an image processing circuit.

[0024] In this specification, the term "semiconductor" refers to all devices that can function by utilizing semiconductor properties. Also called semiconductor devices, electro-optical devices, semiconductor circuits, and electronic equipment are all semiconductor devices. El. [Effects of the Invention]

[0025] We can provide a liquid crystal display device that can display images according to various ambient light conditions. Furthermore, it is possible to achieve low power consumption when displaying still images. [Brief explanation of the drawing]

[0026] [Figure 1] A block diagram illustrating one form of liquid crystal display device. [Figure 2] A diagram illustrating one form of liquid crystal display device. [Figure 3] A diagram illustrating one method of driving a liquid crystal display device. [Figure 4] A diagram illustrating one method of driving a liquid crystal display device. [Figure 5] A diagram illustrating one method of driving a liquid crystal display device. [Figure 6] A diagram illustrating one form of liquid crystal display device. [Figure 7] A diagram illustrating one form of liquid crystal display device. [Figure 8] A diagram illustrating one form of liquid crystal display device. [Figure 9] A diagram illustrating one form of liquid crystal display device. [Figure 10]A diagram illustrating one form of liquid crystal display device. [Figure 11] A diagram illustrating one form of transistor applicable to liquid crystal display devices. [Figure 12] A diagram illustrating one method for fabricating transistors applicable to liquid crystal display devices. [Figure 13] A diagram illustrating one form of electronic device. [Figure 14] A diagram illustrating one form of liquid crystal display device. [Figure 15] A diagram illustrating one form of liquid crystal display device. [Figure 16] A diagram illustrating one form of liquid crystal display device. [Modes for carrying out the invention]

[0027] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is... Not limited to the following description, the form and details can be modified in various ways, as any person skilled in the art would know. This is easily understood. Furthermore, the present invention shall be interpreted as being limited to the contents of the embodiments described below. It's not something that can be done.

[0028] (Embodiment 1) In this embodiment, Figure 1 is used to describe a liquid crystal display device having a still image mode and a video mode. This will be explained. In this specification, the image signal that the display device inputs to the display device is a still image. The actions performed based on the determination that it is a still image are called still image mode, and the actions performed based on the determination that it is a video are called video mode. Let's assume that.

[0029] The liquid crystal display device 100 of this embodiment includes an A / D conversion circuit 102, an image processing circuit 110, and a display. It has a display panel 120 and a backlight unit 130 (see Figure 1).

[0030] The image processing circuit 110 includes a memory circuit 111, a comparison circuit 112, a selection circuit 115, and a display control circuit. It has a path 113 and a field sequential signal generation circuit 114.

[0031] The display panel 120 has a drive circuit 121 and a pixel section 122. The pixel section 122 is a picture It has elements 123, and the pixels 123 are connected to the first set of scan lines and the first set of signal lines. One sub-pixel 123a, and connected to the second scan line and the second signal line. It has a second system of subpixels 123b. Also, subpixels 123a and subpixels 123b These are paired and arranged in a matrix-like manner as multiple pixels 123 in the pixel section 122.

[0032] Furthermore, the sub-pixel 123a is connected to a first transistor and an image connected to the first transistor. It has a primary electrode and a capacitive element. A liquid crystal layer is sandwiched between the pixel electrode and the opposing electrode. A liquid crystal element is formed therein, and the pixel electrode is light-transmitting. In this context, electrodes that have the ability to transmit visible light are also called transparent electrodes. .

[0033] Furthermore, sub-pixel 123b is connected to a second transistor and an image connected to the second transistor. It has a primary electrode and a capacitive element. A liquid crystal layer is sandwiched between the pixel electrode and the opposing electrode. A liquid crystal element is formed therein, and the pixel electrode reflects incident light through the liquid crystal layer.

[0034] One example of a liquid crystal element is one that controls the transmission or non-transmission of light through the optical modulation effect of liquid crystals. There is an element. This element can be constructed from a pair of electrodes and a liquid crystal layer. The optical modulation effect of liquid crystals is controlled by the electric field (i.e., the vertical electric field) applied to the liquid crystal. Specifically, examples of liquid crystal elements include nematic liquid crystals and cholesteric liquid crystals. Smectic liquid crystal, discotic liquid crystal, thermotropic liquid crystal, lyotropic liquid crystal, Low molecular weight liquid crystals, polymer liquid crystals, polymer dispersed liquid crystals (PDLCs), ferroelectric liquid crystals, antiferroelectric liquid crystals, Examples include main-chain liquid crystals, side-chain polymer liquid crystals, and banana-shaped liquid crystals. The operating modes include TN (Twisted Nematic) mode and STN (Super Twisted Nematic mode, OCB (Optically Competitive) (Insulated Birefringence) mode, ECB (Electric All) (Controlled Birefringence) mode, FLC (Ferro electric Liquid Crystal) mode, AFLC (AntiFer PDLC (Polymer Liquid Crystal) mode, Dispersed Liquid Crystal (PNLC) mode, Pol YMER Network Liquid Crystal) mode, guest host mode There are others, such as Do.

[0035] The backlight section 130 includes a backlight control circuit 131 and a backlight 132. The backlight 132 has light-emitting elements 133 arranged on it.

[0036] In this embodiment, the backlight 132 has multiple light-emitting elements 133 of different light-emitting colors. For example, combinations of different luminescent colors include red (R), green (G), and blue (B). Three types of light-emitting elements can be used. By using the three primary colors R, G, and B, full It can display color images.

[0037] In addition, colors can be expressed by simultaneously illuminating multiple selected R, G, and B light-emitting elements (for example, Yellow (Y) is represented by R and G, cyan (C) by G and B, magenta (M) by B and R, etc. Another light-emitting element that emits light may be placed in addition to the R, G, and B light-emitting elements.

[0038] Furthermore, in order to enrich the color reproduction characteristics of the display device, light-emitting elements that emit light other than the three primary colors are used. They may also be added. The colors that can be represented using R, G, and B light-emitting elements are, respectively, on the chromaticity diagram. The colors shown are limited to those within the triangle formed by the three points corresponding to the emission color. Therefore, on the chromaticity diagram... By adding a light-emitting element positioned outside the triangle, the color reproduction characteristics of the display device can be enriched. It can be done.

[0039] For example, from the center of the chromaticity diagram, outward towards the point corresponding to the blue light-emitting element B on the chromaticity diagram. Deep blue (DB) represented by a specific coordinate point, or the center of the chromaticity diagram. From there, at a coordinate point located outward from the point on the chromaticity diagram corresponding to the red light-emitting element R A light-emitting element that emits a deeper red (Deep Red: DR) than the one shown is used in the backlight 1. It can be used in addition to 32 R, G, and B.

[0040] Next, the signal flow in the display device illustrated in this embodiment will be described.

[0041] An analog image signal 140 is input to the liquid crystal display device 100 from the image signal supply source 101. Analog image signals include image signals, such as red (R), green (G), and blue (B). The signal is included.

[0042] The A / D conversion circuit 102 converts the analog image signal to a digital image signal 141 (digital image signal The image signal is converted to a digital signal (Data) and output to the image processing circuit 110. Converting the image signals beforehand makes it easier to detect differences in the image signals later on. It is suitable.

[0043] The image processing circuit 110 processes the input digital image signal Data into an LC image signal 142 and a It generates a light signal 143. The LC image signal 142 controls the display panel 120. The image signal is the backlight signal 143, and the backlight signal 143 is a signal that controls the backlight unit 130. .

[0044] The memory circuit 111 provided in the image processing circuit 110 stores image signals related to multiple frames. It has multiple frame memories for this purpose. The number of frame memories that the memory circuit 111 has It is not particularly limited to any element that can store image signals for multiple frames. That's all you need to do. Note that frame memory is, for example, DRAM (Dynamic Random A). ccess Memory), SRAM (Static Random Access It can be constructed using memory elements such as Memory.

[0045] The frame memory can be configured to store the image signal for each frame period. There are no particular limitations on the number of memory slots. Also, the image signal in the frame memory is... These are selectively read out by the comparison circuit 112 and the display control circuit 113.

[0046] The comparison circuit 112 selects image signals from consecutive frame periods stored in the memory circuit 111. The data is read out sequentially, and the corresponding image signal is compared pixel by pixel between consecutive frames, and the difference is detected. This is a circuit for outputting data.

[0047] The operation of the display control circuit 113 and the selection circuit 115 is determined by whether or not a difference is detected. This will be done. By comparing the image signals in the comparison circuit 112, any difference will be found in any pixel. When minutes are detected, the consecutive frame period in which the difference was detected is determined to be the video period. On the other hand, by comparing the image signals in the comparison circuit 112, differences are detected in all pixels. If no difference is detected during this process, consecutive frame periods will be determined to be still image periods. In other words, the comparison circuit 112 processes the image signal for a continuous frame period using the comparison circuit 112. By detecting the difference, it is determined whether the signal is an image signal for displaying a video or a still image. This determines whether the signal is an image signal.

[0048] Furthermore, when the difference obtained through this comparison exceeds a certain level, a difference is detected. It may be configured to make such a judgment. Note that the comparison circuit 112 will, regardless of the magnitude of the difference, The setting should be configured to determine whether a difference has been detected based on its absolute value.

[0049] In this embodiment, the comparison circuit 112 analyzes the image signal over a continuous frame period. We have shown a configuration that determines whether something is a video or a still image by detecting the difference, but external By supplying a signal to switch between still images and video, the system responds to the signal to be switched. The system may also be configured to display video or still images.

[0050] Furthermore, video works by rapidly switching between multiple images that are time-divided into multiple frames, which is how the human eye perceives it. This refers to an image that is recognized as moving. Specifically, for example, 60 frames per second (60 frames). By switching between images (more than 100), the human eye perceives the image as less flickering and as a video. On the other hand, unlike video, still images are time-divided into multiple frames. Although it switches and operates at high speed, it does not operate over consecutive frame periods, for example, the nth frame and This refers to an image signal that does not change from the (n+1)th frame onwards.

[0051] The selection circuit 115 includes multiple switches, such as switches formed by transistors. The configuration is as follows: When a difference is detected by the difference calculation in the comparison circuit 112, that is, a continuous When the image displayed between frames is a video, the image signal stored in the memory circuit 111 This circuit selects an image signal from the frame memory and outputs it to the display control circuit 113. ru.

[0052] Furthermore, when the comparison circuit 112 does not detect a difference in the image signals, the selection circuit 115 is used. In other words, when an image is displayed between consecutive frames, the image signal is displayed as a still image. This circuit does not output to control circuit 113. When a still image is captured, the selection circuit 115 outputs the image signal. By configuring the frame memory not to output to the display control circuit 113, power consumption is reduced. It can be reduced.

[0053] In addition, in the display device of this embodiment, the comparison circuit 112 determines that it is a still image and performs the following action The operation performed when the image is created is called still image mode, and the operation performed when the comparison circuit 112 determines it to be a video is called video mode.

[0054] Furthermore, the image processing circuit illustrated in this embodiment may also have a mode switching function. The mode switching function can be operated manually or by using an external device to switch modes. The device switches between video mode and still image mode by selecting the operating mode of the display device. It is Noh.

[0055] Therefore, the display device illustrated in this embodiment may have a mode switching circuit. The mode switching circuit is connected to the selection circuit 115. The user of the display device can switch the operating mode of the display device manually or using an externally connected device. It is an input method for obtaining information.

[0056] The selection circuit 115 controls the display of the image signal according to the signal input from the mode switching circuit. It can also output to circuit 113.

[0057] For example, when operating in still image mode, if the user switches the operating mode, the mode will turn off. When a mode switching signal is input from the switching circuit to the selection circuit 115, the comparison circuit 112 Even if the selection circuit does not detect the difference in image signals over consecutive frame periods, 115 is a mode in which the input image signal is sequentially output to the display control circuit 113, i.e., video. The mode can be executed. Also, when operating in video mode, the user can switch the operating mode. Alternatively, when a mode switching signal is input from the mode switching circuit to the selection circuit 115: In the case where the comparison circuit 112 detects the difference in image signals over consecutive frame periods, However, the selection circuit 115 is in a mode that outputs only the image signal of the selected 1 frame. In other words, it can execute still image mode. Therefore, the display device of this embodiment can execute video display mode. When running in a D-system, one of the images, which is time-divided into multiple frames, is a still image. It will be displayed as follows.

[0058] The display control circuit 113 is selected by the selection circuit 115 in response to the detection of a difference in the comparison circuit 112. This circuit optimizes the received image signal for the display panel 120 and the backlight unit 130. ru.

[0059] For example, even if the digital image signal 141 consists of R, G, and B signals, The image signal is optimized to match the light emission characteristics of the R, G, and B light-emitting elements of the Krite 132. It is preferable to modify the backlight 132 to include light-emitting elements other than R, G, and B. If provided, the display control circuit 113 generates a signal from the original image signal to drive the light-emitting element. It generates and optimizes the color reproduction characteristics of the display device.

[0060] For example, a digital image signal Data(1) consisting of R, G, and B is divided into R, G, B, DR , and a digital image signal Da suitable for a backlight 132 equipped with five light-emitting elements of DB. When converting to ta(4), the display control circuit 113 converts the original digital image signal Data(1 ) generates a digital image signal Data(2) represented using the light-emitting element DR and DB. To accomplish this, simultaneously, the light-emitting element DR and DB are used from the original digital image signal Data(1). Subtract the digital image signal Data(2) which is expressed as the digital image signal Data( 3) is generated. Next, a digital image signal D is represented using the light-emitting element DR and DB. ata(2) and the digital image signal Data( represented using light-emitting elements R, G, and B) 3) A backlight 132 equipped with five light-emitting elements of R, G, B, DR, and DB. It generates a digital image signal Data(4) optimized for this purpose.

[0061] Furthermore, the display device illustrated in this embodiment is connected to the first signal line It has a main pixel 123a and a second sub-pixel 123b connected to a second signal line. The display control circuit 113 then determines the signal line to output the image signal.

[0062] Specifically, the display control circuit 113, when the comparison circuit 112 determines that it is a video, outputs an image signal The first sub-pixel 123a outputs the signal, and if the comparison circuit 112 determines it to be a still image, the image is output. The image signal is output to the second sub-pixel 123b.

[0063] The field sequential signal generation circuit 114 generates image signals generated by the display control circuit 113. Based on the number, the drive circuit 121 of the display panel 120 and the backlight section 130 This is a circuit for controlling the control circuit 131.

[0064] Furthermore, the field sequential signal generation circuit 114 is connected to the display panel 120 and backlight. The start pulse SP and control signals such as the clock signal CK are supplied to synchronize the unit 130. It also serves as a circuit to control the switching between stopping and starting.

[0065] Next, the field sequential signal generation circuit 114 drives the display panel 120. 21. A method for controlling the backlight control circuit 131 of the backlight unit 130. Let me explain. The operation of the field sequential signal generation circuit 114 is shown in the video by the comparison circuit 112. The system behaves differently depending on whether it determines it to be an image or a still image. The number consists of R, G, and B, and the backlight 132 is a light-emitting element of R, G, and B (specifically It shall have an LED.

[0066] First, when the comparison circuit 112 determines that it is a video, the field sequential signal generation cycle The operation of path 114 will be explained. The field sequential signal generation circuit 114 is Image signals, including images, are processed in video mode. Specifically, field sequential signals... The signal generation circuit 114 outputs the image signals optimized by the display control circuit 113 to the time axis. Then it is compressed to 1 / (3n) times its original size. Note that n is the number of subframes into which one frame is divided. It is equivalent to the n used in the case of [the example]. And it is compressed to 1 / (3n) times with respect to the time axis. Field sequential color image signals corresponding to R, G, and B (for example, R1, G1 The following are supplied to the drive circuit 121: B1, R2, G2, B2).

[0067] Furthermore, the field sequential signal generation circuit 114 generates the backlight signal 143 from the backlight signal 143. The signal is supplied to the light 132. The backlight signal 143 is supplied to the R provided in the backlight 132. This is a signal that lights up the light-emitting elements R, G, and B, and corresponds to the field sensor of R, G, B. This signal is paired with the chromatic color image signal.

[0068] Furthermore, the display panel 120 and the backlight unit 130 generate field sequential signals. The system operates in sync with the synchronization signal emitted by circuit 114, and the video is displayed.

[0069] On the other hand, if the comparison circuit 112 determines that the image signal is a still image, the field sequential signal The signal generation circuit 114 does not generate a field sequential color image signal, but only for one frame. The still image data is supplied to the drive circuit 121 of the display panel 120.

[0070] Subsequently, the field sequential signal generation circuit 114 controls the drive circuit 121 and the back The supply of the image signal and each control signal to the light control circuit 131 is stopped.

[0071] Furthermore, the display device illustrated in the embodiment may also have a photometric circuit. The digit display device can detect the brightness of the environment in which it is placed. As a result, photometry is performed. The display control circuit 113, to which the circuit is connected, controls the display in accordance with the signal input from the photometric circuit. The drive method of the Nel 120 can be changed.

[0072] For example, the photometering circuit is used when the display device exemplified in this embodiment is used in a dimly lit environment. When this is detected, the display control circuit 113, if the comparison circuit 112 has determined that it is a still image, However, the image signal is output to the first sub-pixel 123a, and the backlight 132 is turned on. The first sub-pixel 123a has a light-transmitting pixel electrode, so the backlight... It can provide still images with high visibility.

[0073] Furthermore, for example, the photometric circuit is configured such that the display device exemplified in this embodiment is exposed to extremely bright ambient light. For example, if it detects that it is being used outdoors in direct sunlight, the display control circuit 113 will Even if the comparison circuit 112 determines that it is a video, the image signal is transmitted to the second sub-pixel 123 Output to b. The second sub-pixel 123b is a pixel that reflects light incident through the liquid crystal layer. Because it has electrodes, it produces highly visible still images and videos even in extremely bright ambient light. It can be used.

[0074] During the period when a still image is displayed according to the configuration of this embodiment, the image signal is written frequently. This reduces the need for such operations. Furthermore, it allows for the display of still images without using the backlight. Therefore, it consumes very little power.

[0075] Furthermore, the display device exemplified in this embodiment can display still images while reducing power consumption. Furthermore, it allows for the display of full-color images and videos without the use of color filters. It is possible. Because the color filter does not absorb the backlight, the light utilization efficiency is high. Power consumption is suppressed even when displaying full-color images and videos.

[0076] Furthermore, when viewing an image created by writing multiple image signals, the image switches multiple times. The human eye perceives these images. Therefore, this manifests as eye fatigue. This is also possible. As described in this embodiment, a configuration that reduces the number of times the image signal is written and This also has the effect of reducing eye strain.

[0077] This embodiment can be appropriately combined with other embodiments shown herein. .

[0078] (Embodiment 2) In this embodiment, the driving method of the liquid crystal display device is determined using a pixel connection diagram, timing chart, etc. Let me explain the law. First, Figure 2 shows a schematic diagram of the display panel of a liquid crystal display device. Figure 2 shows the pixel section 151, the first scan line 152 (also called the gate line), and the first signal. Line 153 (also called data line), second scan line 154, second signal line 155, pixel 156 , common electrode 169 (also called common electrode), capacitance line 170, first scan line drive circuit 157 , first signal line drive circuit 158, second scan line drive circuit 159, second signal line drive circuit 1 It has 60.

[0079] The pixel 156 is broadly divided into a transmissive electrode section 161 and a reflective electrode section 162. The transmissive electrode section 161 is It has a pixel transistor 163, a liquid crystal element 164, and a capacitive element 165. The gate of 163 is connected to the first scan line 152 and is either the source or the drain. One terminal is connected to the first signal line 153, and the second terminal, which is either the source or the drain, It is connected to one electrode of the liquid crystal element 164 and the first electrode of the capacitive element 165. The other electrode of sub-electrode 164 is connected to the common electrode 169. The electrodes are connected to capacitance wire 170.

[0080] Furthermore, the reflective electrode section 162 contains the pixel transistor 166, the liquid crystal element 167, and the capacitive element 168. It has. The pixel transistor 166 has a gate connected to the second scan line 154, and a source or One of the drain terminals, the first terminal, is connected to the second signal line 155, and the source or drain The other second terminal is connected to one electrode of the liquid crystal element 167 and the first electrode of the capacitive element 168. The connection is made. The other electrode of the liquid crystal element 167 is connected to the common electrode 169. The second electrode of the capacitive element 168 is connected to the capacitance line 170.

[0081] In Figure 2, the first scan line 152 and the second scan line 154 are the first scan line drive cycles. The first signal line 157 and the second scan line drive circuit 159 are driven separately. 53 and the second signal line 155 are connected to the first signal line drive circuit 158 ​​and the second signal line drive circuit 160 supplies separate image signals (hereinafter referred to as the first data and the second data). And the liquid crystal element 164 of the transparent electrode part 161 and the liquid crystal element 16 of the reflective electrode part 162 In version 7, gradation control is performed based on different image signals.

[0082] Furthermore, pixel transistors 163 and 166 have a thin oxide semiconductor layer. It is preferable to use thin-film transistors (hereinafter also referred to as TFTs).

[0083] Furthermore, a thin-film transistor has at least three terminals, including the gate, drain, and source. It is an element having a drain region and a channel region between the drain region and the source region, Current can be passed through the rain region, channel region, and source region. Here, The terms "sow" and "drain" vary depending on the transistor's structure and operating conditions, so which one is the drain? It is difficult to determine whether it is a drain or a pipe. Therefore, this document (specification, special In the scope of the claims or drawings, etc., the areas that function as source and drain are defined as follows: They are sometimes not called drains or suctions. In that case, for example, each is called the first They are sometimes referred to as terminal and second terminal. Alternatively, they may be referred to as first electrode and second electrode, respectively. These terms may be used. Alternatively, they may be referred to as source area and drain area.

[0084] Furthermore, the first scan line drive circuit 157, the first signal line drive circuit 158, and the second scan line drive circuit 159. The second signal line driving circuit 160 is configured to be provided on the same substrate as the pixel unit 151. While this is preferable, it is not necessarily required to provide the pixel section 151 on the same substrate. On the same circuit board as 1, a first scan line drive circuit 157, a first signal line drive circuit 158, and a second drive circuit By providing a signal line drive circuit 159 and a second signal line drive circuit 160, the number of connection terminals to the outside is reduced. This can reduce the size of liquid crystal displays, making them more compact.

[0085] Note that the pixels 156 are arranged (arranged) in a matrix. Here, the pixels are matrix Arranged in a grid means that the pixels are aligned in a straight line, either vertically or horizontally. This includes cases where they are positioned on a grid or on a jagged line.

[0086] Furthermore, if it is explicitly stated that A and B are connected, it means that A and B are electrically connected. When A and B are functionally connected, and when A and B are directly connected This includes cases where this is the case.

[0087] Next, the operation of the display panel, along with the operation of the backlight, will be explained in Figure 3(A). To clarify, as explained in the above embodiment, the operation of the display panel can be broadly divided into two categories: video display It is broadly divided into display period 301 and still image display period 302.

[0088] Furthermore, in video display period 301, the period of one frame (or frame frequency) is: It is desirable that the frame rate be 1 / 60th of a second or less (60Hz or higher). This prevents viewers from experiencing flickering when viewing images. In the image display period 302, the period of one frame is made extremely long, for example, more than 1 minute (0. By setting the frequency to 0.17Hz or lower, compared to switching the same image multiple times... It may also be possible to reduce eye strain.

[0089] Furthermore, the semiconductor layer of pixel transistors 163 and 166 is an oxide semiconductor. When using this method, the off-current can be reduced. Therefore, the image signal at the pixel The holding time of electrical signals such as these can be extended, and the writing interval can also be set to be longer. The period of one frame can be lengthened, and the refresh rate during the still image display period 302 can be increased. Because the frequency of operation can be reduced, the effect of reducing power consumption can be further enhanced.

[0090] In the video display period 301 shown in Figure 3(A), as described in the above embodiment, the feel The drive circuit control signal for displaying video using sequential drive is the first scan line drive. It is supplied to circuit 157 and the first signal line drive circuit 158 ​​(hereinafter referred to as the first drive circuit). The drive circuit control signal for displaying black on each pixel is the second scan line drive circuit 159 and It is supplied to the second signal line drive circuit 160 (hereinafter referred to as the second drive circuit) and the first drive circuit And the second drive circuit operates. Also, during the video display period 301 shown in Figure 3(A), Fee The backlight signal 143 for color display is driven sequentially. The backlight is powered, and the backlight operates. The display panel then displays in color. Image display is possible.

[0091] In the still image display period 302 shown in Figure 3(A), as described in the above embodiment, reflected light Because the black and white gradation (indicated as BK / W in the diagram) is represented by the transparency or opacity of the element, static A control signal for the drive circuit that writes the image signal of the picture is supplied to the second drive circuit, and the second drive The drive circuit operates. Note that the second drive circuit is the drive circuit for periods other than when writing the image signal. By disabling the control signal, power consumption can be reduced. Also, as shown in Figure 3(A) During the still image display period 302, the display is made visible by utilizing reflected ambient light, The backlight control signal disables the backlight. The display panel then displays in black and white. It is possible to display still images of the tone.

[0092] Next, regarding the video display period 301 in Figure 3(A), Figure 3(B) shows the still image display period 302 Figure 3(C) provides a detailed explanation of this using a timing chart. Note that Figures 3(B) and The timing chart shown in Figure 3(C) is exaggerated for illustrative purposes. Unless otherwise specified, it should be noted that the signals do not operate in synchronous manner.

[0093] First, let's explain Figure 3(B). In Figure 3(B), as an example, the video display period is 301. The clock signal supplied to the first scan line drive circuit 157 and the second scan line drive circuit 159 GCK (GCK1,2 in the figure), and start pulse GSP (GSP1,2 in the figure), Clock signal S supplied to the first signal line drive circuit 158 ​​and the second signal line drive circuit 160 CK (SCK1,2 in the figure), and start pulse SSP (SSP1,2 in the figure), 1 This shows the first data, the second data, and the backlight illumination status. As a backlight, one example is a configuration that sequentially illuminates the three RGB colors as multiple light-emitting elements. I will now explain this. Furthermore, LEDs are used as the backlight to reduce power consumption. This allows for electrification and extension of the lifespan.

[0094] During the video display period 301, the clock signals GCK1 and GCK2 are continuously supplied clock signals. This is how it works. Also, the start pulses GSP1 and GSP2 are pulses corresponding to the vertical synchronization frequency. The clock signals SCK1 and SCK2 are constantly supplied clock signals. Also, the start pulse... SSP1 and SSP2 will be pulses corresponding to the gate selection period. Note that during the video display period 301, To display video in field sequential mode, the image signal is first displayed as R (red). Next, writing to each pixel, then turning on the R (red) backlight, and then displaying the G (green) color. Next, writing to each pixel, then turning on the G (green) backlight, and then displaying the B (blue) color. The image signal is varied by repeatedly writing to each pixel, followed by turning on the backlight of B. This allows viewers to see the color display in the video. Also, the video display period is 3 In 01, the second data is an image signal for displaying the BK (black) gradation, and pixel 1 The data is written to the reflective electrode section 162 of 56. The second data is an image to display black. By converting it into an image signal, ambient light is irradiated onto the reflective electrode section 162. This causes light leakage. This improves the visibility of the video of the transparent electrode section 161, which is reduced in visibility. Cut.

[0095] Next, Figure 3(C) will be explained. In Figure 3(C), regarding the still image display period 302, The explanation will be divided into still image writing period 303 and still image retention period 304.

[0096] During the still image writing period 303, the clock supplied to the second scan line drive circuit 159 Signal GCK2 is the clock signal for writing one screen. Also, the second scan line drive circuit 1 The start pulse GSP2 supplied to 59 is the pulse for writing one screen. The clock signal SCK2 supplied to the signal line drive circuit 160 is a clock signal for writing one screen. This becomes a buck signal. Also, the start pulse SSP2 supplied to the second signal line drive circuit 160, This becomes a pulse for writing to one screen. Note that reflected light is used during the still image writing period 303. To display a still image using the BK / W image signal for displaying grayscale tones, color The backlight used for displaying the screen will not illuminate.

[0097] During the still image holding period 304, the first drive circuit and the second drive circuit are driven Clock signals GCK1,2, start pulses GSP1,2, clock signals SCK1,2, The start pulses SSP1 and SSP2 will be stopped from being supplied. Therefore, the still image retention period will be affected. In the 304 model, power consumption can be reduced, resulting in lower power consumption. During the image retention period 304, the image signals written to the pixels during the still image writing period 303 are turned off. Because it is held by pixel transistors with extremely low current, a still image of a color display can be held for 1 minute. It can be held for the above period. Also, the still image holding period 304 is held in the capacitor. Before the image signal changes due to the passage of a certain period of time, a new still image writing period 303 is created. The same image signal as the image signal from the previous period is written (refresh operation), and the still image is restored. The retention period should be set to 304.

[0098] The liquid crystal display device described in this embodiment aims to reduce power consumption when displaying still images. It is possible.

[0099] This embodiment can be implemented in appropriate combination with the configuration described in Embodiment 1. be.

[0100] (Embodiment 3) In this embodiment, the driving method for the liquid crystal display device described in Embodiment 2 above is different from the configuration described above. This will be explained using timing charts, etc. First, Figure 4(A) shows the above embodiment. The method for driving the backlight during the video display period 301 as explained in 2 is a timing chart. Show and explain.

[0101] The difference between the timing chart in Figure 4(A) and Figure 3(B) is that the image signal writing is followed by... Furthermore, after the backlight is turned on, a period of time when the backlight is off (BL in Figure 4(A)) is provided. It is located at a specific point. A period of time should be provided during which the backlight is turned off before writing the next image signal. This reduces color flicker and improves visibility.

[0102] Figure 4(B) shows a configuration different from that in Figure 4(A). The difference between T and Figure 4(A) is that the backlight off period BL is replaced with the light-emitting period of B (blue). The key is the inclusion of a gap. By introducing a blue light emission period before writing the next image signal, Similar to the case where the lights are turned off for a period of time, this can reduce color flicker and improve visibility. Cut.

[0103] Furthermore, in the above embodiment 2, as an example of multiple light-emitting elements used for the backlight, RGB We have explained an example using these three colors, but other configurations are also possible. As an example, see Figure 5(A) As shown, the backlight may be controlled using five colored light-emitting elements 311. .

[0104] As an example, the light-emitting element 311 shown in Figure 5(A) includes a first red light-emitting element R1 and a second red light-emitting element. Regarding the light-emitting element R2, the green light-emitting element G, the first blue light-emitting element B1, and the second blue light-emitting element B2... This is shown. Next, in Figure 5(B), the above practical example is shown in the same manner as in Figures 4(A) and (B). During the video display period 301 as described in Method 2, the backlight is illuminated as shown in Figure 5(A). Let's explain the control system.

[0105] In Figure 5(B), following the writing of the R image signal, the first red light is turned on as the backlight. The color light-emitting element R1 and the first blue light-emitting element B1 are illuminated. Also, the image signal G is written. Following this, the green light-emitting element G and the second blue light-emitting element B2 were illuminated as the backlight. The light is turned on. Also, following the writing of the image signal B, the first blue light is turned on as the backlight. The first color light-emitting element B1 and the second blue light-emitting element B2 are turned on. Then, the image signal of R is written. Following this, the second red light-emitting element R2 and the second blue light-emitting element were used to illuminate the backlight. The sub-B2 is turned on. Also, the backlight is turned on following the writing of the image signal to G. The green light-emitting element G and the blue light-emitting element B1 are then lit. Also, the image signal of B is written. Following this, the second blue light-emitting element B2 and the first blue light-emitting element were used to illuminate the backlight. Turn on the B1 light.

[0106] By using the configuration shown in Figure 5(B), the blue light emission period occurs during the period when the RGB color elements switch. Since this can be provided, the same effect as in Figure 4(B) can be obtained. Also, the first red light emission Element R1 and second red light-emitting element R2, first blue light-emitting element B1 and second blue light-emitting element B2 , it also becomes possible to use light-emitting elements made of materials with different color coordinates, in color display It can expand the range of color expression.

[0107] The liquid crystal display device described in this embodiment aims to reduce power consumption when displaying still images. It is possible.

[0108] This embodiment can be implemented in appropriate combination with the configuration described in Embodiment 1. be.

[0109] (Embodiment 4) Figure 6 shows the configuration of the liquid crystal display module 190. The liquid crystal display module 190 has a backlight. The unit 130, the display panel 120 in which liquid crystal elements are arranged in a matrix, and the display panel 1 It has polarizing plates 125a and 125b that sandwich 20. The backlight section 130 has Light-emitting elements, such as the three primary color LEDs (133R, 133G, and 133B), arranged in a matrix. The backlight is positioned with the diffuser plate 134 placed between the display panel 120 and the light-emitting element. It can be used as part 130. It can also be used as an external input terminal (FPC (flexible printed circuit board)). The 126 (Lupin Circuit) is electrically connected to the terminal section provided on the display panel 120. Yes, they are.

[0110] Figure 6 schematically shows the three colors of light 135 with arrows (R, G, and B). The pulsed light of different colors emitted sequentially from the light unit 130 synchronizes with the backlight unit 130. The liquid crystal elements of the display panel 120, which operate in this manner, are modulated by the liquid crystal display module 190. The light then reaches the observer. The observer captures the sequentially emitted light as an image.

[0111] Furthermore, Figure 6 shows that ambient light 139 passes through the liquid crystal element on the display panel 120 and reaches its lower electrode. The reflection process is also schematically shown. The intensity of light transmitted through the liquid crystal element depends on the image signal. Because it is modulated, the observer can also capture the image using reflected ambient light 139. .

[0112] Figure 7(A) is a plan view of the display area, and Figure 7(B) is an equivalent circuit, showing one pixel. Figure 8 shows the cross-sections along lines V1-V2, W1-W2, and X1-X2 in Figure 7(A). This is a diagram.

[0113] In Figure 7, multiple source wiring layers (source electrode layer or drain electrode layer 555b, 565) (including b) are arranged parallel to each other (extending vertically in the figure) and spaced apart from each other. Multiple gate wiring layers (including gate electrode layer 551) are arranged approximately perpendicular to the source wiring layer. They extend in the direction (left-right in the diagram) and are arranged to be spaced apart from each other. They are positioned adjacent to each of the multiple gate wiring layers, and are roughly parallel to the gate wiring layers. It extends in a horizontal direction, that is, in a direction roughly perpendicular to the source wiring layer (left-right direction in the diagram).

[0114] The liquid crystal display devices in Figures 7 and 8 are semi-transmissive liquid crystal display devices, and the pixel area is the reflective area 49 It consists of 8 and a transmission region 499. In the reflection region 498, the reflective electrode is used as the pixel electrode layer. Layer 577 is formed, and in the transparent region 499, a transparent electrode layer 576 is formed as a pixel electrode layer. As shown in Figures 7 and 8, the transparent electrode layer 576 and the reflective electrode layer 577 are separated by an insulating film 571. When stacked so that their edges overlap via a barrier, the display area can be efficiently created within the pixel region. It can be done. In Figure 8, a transparent electrode layer 576 and an insulating film 57 are placed on the interlayer film 413. 1. An example is shown in which the reflective electrode layers 577 are stacked in that order, but the reflective electrode layer 57 is placed on the interlayer film 413. 7. The structure may also consist of a laminated insulating film 571 and a transparent electrode layer 576 in that order.

[0115] As shown in Figure 7(B) of the equivalent circuit, a reflective electrode layer 577 and a source electrode layer or A transistor 560 electrically connected to the drain electrode layer 565b, and a transparent electrode layer 576 and and the transistor 550 which is electrically connected to the source electrode layer or drain electrode layer 555b It has. Transistor 560 is a reflection region transistor that controls the on / off switching of the reflection region. Transistor 550 is a transistor for the transparent region that controls the on / off switching of the transparent region. That is the case.

[0116] Insulating films 407 and 409, and an interlayer film 413 are provided on transistors 550 and 560. In each opening (contact hole) formed in the insulating film 407, 409 and the interlayer film 413 In this configuration, transistor 550 has a transparent electrode layer 576, and transistor 560 has a reflective electrode layer 5 Each of the 77s is electrically connected.

[0117] As shown in Figure 8, a common electrode layer (also called a counter electrode layer) 448 is formed on the second substrate 442. A transparent electrode layer 576 and a reflective electrode layer 577 are formed on the first substrate 441, and a liquid crystal layer 444 They are facing each other via a barrier. In addition, in the liquid crystal display devices shown in Figures 7 and 8, the transparent electrode layer 576 and An alignment layer 460a is provided between the reflective electrode layer 577 and the liquid crystal layer 444, and a common electrode layer 448 Alignment films 460b are provided between the liquid crystal layer 444 and the liquid crystal layer 444. Alignment films 460a, 460b This is an insulating layer that has the function of controlling the orientation of liquid crystals, and depending on the liquid crystal material, it may not be necessary to provide it. good.

[0118] Transistors 550 and 560 are examples of inverse staggered transistors with a bottom gate structure. The transistor 550 consists of a gate electrode layer 551, a gate insulating layer 402, and a semiconductor layer 553. Source electrode layer or drain electrode layer 555a, and source electrode layer or drain electrode layer 555 Including b, transistor 560 has a gate electrode layer 551, a gate insulating layer 402, and a semiconductor layer 563, source electrode layer or drain electrode layer 565a, and source electrode layer or drain electrode It includes layer 565b. Also, transistors 550 and 560 each have capacitance, as shown in the figure. As shown in 8, in the reflection region 498, the gate electrode layer 551 and the layer formed in the same process A wiring layer 558, a gate insulation layer 402, and a source electrode layer or drain electrode layer 555a, 555b, 565a, and the conductive layer 579 formed in the same process as 565b are stacked to form capacitance. Furthermore, aluminum (Al) and silver (Ag) are used to cover the capacitance wiring layer 558. A reflective electrode layer 577 is formed from a reflective conductive film, and a wiring layer 580 is formed in the same process. It is preferable to do so.

[0119] The semi-transmissive liquid crystal display device in this embodiment is controlled by the on / off control of the transistor 550. In the transparent region 499, the video is displayed in color, and the on / off control of transistor 560 is performed. Depending on the settings, the monochrome (black and white) display of the still image will be performed in the reflective area 498. By operating transistor 550 and transistor 560 separately, the reflection region 49 The display of 8 and the display of the transparent area 499 can be controlled independently.

[0120] In the transparent region 499, incident light from the backlight provided on the first substrate 441 side The display is created by using RGB light-emitting diodes (LEDs) for the backlight. Color display is possible. Furthermore, in this embodiment, light-emitting diodes (LEDs) This method uses a time-division color mixing method (field sequential method) to display colors. We will adopt this.

[0121] On the other hand, in the reflective region 498, ambient light incident from the second substrate 442 side is reflected by the reflective electrode layer 5 The display is achieved by reflecting light using 77.

[0122] In a liquid crystal display device, examples of forming irregularities on the reflective electrode layer 577 are shown in FIGS. 9 and 10. FIG. 9 shows an example of forming an irregular shape on the reflective electrode layer 577 by making the surface of the interlayer film 413 have an irregular shape in the reflection region 498. The irregular shape on the surface of the interlayer film 413 may be formed by selectively performing etching. For example, a photosensitive organic resin may be subjected to photolithography to form an interlayer film 413 having an irregular shape. FIG. 10 shows an example of forming an irregular shape on the reflective electrode layer 577 by providing a convex structure on the interlayer film 413 in the reflection region 498. Note that FIG. 10 shows a convex structure formed by laminating the insulating layer 480 and the insulating layer 482. For example, an inorganic insulating layer such as silicon oxide or silicon nitride may be used as the insulating layer 480, and an organic resin such as polyimide resin or acrylic resin may be used as the insulating layer 482. First, a silicon oxide film is formed on the interlayer film 413 by sputtering, and a polyimide resin film is formed on the silicon oxide film by coating. The silicon oxide film is used as an etching stopper, and the polyimide resin film is etched. By etching the silicon oxide film using the processed polyimide resin layer as a mask, a convex structure composed of the laminated insulating layer 480 and insulating layer 482 as shown in FIG. 10 can be formed. As shown in FIGS. 9 and 10, when the surface of the reflective electrode layer 577 has irregularities, incident external light can be diffusely reflected, and better display can be achieved. Therefore, the visibility in display is improved. This embodiment can be freely combined with Embodiments 1 to 3 respectively. First, a silicon oxide film is formed on the interlayer film 413 by sputtering, and a polyimide resin film is formed on the silicon oxide film by coating. The silicon oxide film is used as an etching stopper, and the polyimide resin film is etched. By etching the silicon oxide film using the processed polyimide resin layer as a mask, a convex structure composed of the laminated insulating layer 480 and insulating layer 482 as shown in FIG. 10 can be formed. [[ID=(23)]] The silicon oxide film is used as an etching stopper, and the polyimide resin film is etched. By etching the silicon oxide film using the processed polyimide resin layer as a mask, a convex structure composed of the laminated insulating layer 480 and insulating layer 482 as shown in FIG. 10 can be formed. As shown in FIGS. 9 and 10, when the surface of the reflective electrode layer 577 has irregularities incident external light can be diffusely reflected, and better display can be achieved. Therefore, the visibility in display is improved.

[0123] As shown in FIGS. 9 and 10, when the surface of the reflective electrode layer 577 has irregularities, incident external light can be diffusely reflected, and better display can be achieved. Therefore, the visibility in display is improved.

[0124] This embodiment can be freely combined with Embodiments 1 to 3 respectively.​

[0125] (Embodiment 5) This embodiment shows an example of a transistor that can be applied to the liquid crystal display device disclosed herein. The transistor structure applicable to the liquid crystal display devices disclosed herein is not particularly limited. For example, using a top gate structure or a bottom gate structure of staggered and planar type. It is possible. Also, the transistor is a single channel where one channel formation region is formed. Even in a gate structure, a double gate structure is formed with two gates, or a triple gate structure is formed with three gates. It may also be constructed in such a way. In addition, two gate insulating layers are placed above and below the channel region. A dual-gate type with a gate electrode layer is also acceptable. See Figures 11(A) to 11(D) An example of a transistor cross-sectional structure is shown below. Figures 11(A) to 11(D) are shown below. A transistor uses an oxide semiconductor as its semiconductor. The advantage of this is that high mobility and low off-current can be obtained through a relatively simple and low-temperature process. However, other semiconductors may, of course, be used.

[0126] The transistor 410 shown in Figure 11(A) is a thin-film transistor with a bottom gate structure. It is also called an inverse staggered thin-film transistor.

[0127] The transistor 410 has a gate electrode layer 401 and a gate on a substrate 400 having an insulating surface. Insulating layer 402, oxide semiconductor layer 403, source electrode layer 405a, and drain electrode layer 40 It includes 5b. It also covers transistor 410 and is an insulating film stacked on oxide semiconductor layer 403. A layer 407 is provided. An insulating film 409 is further formed on the insulating film 407.

[0128] The transistor 420 shown in Figure 11(B) is a channel protection type (also known as a channel stop type). It is a type of bottom-gate structure called a (u) and is also known as an inverse staggered thin-film transistor.

[0129] The transistor 420 has a gate electrode layer 401 and a gate on a substrate 400 having an insulating surface. The insulating layer 402, the oxide semiconductor layer 403, and the channel formation region of the oxide semiconductor layer 403 Insulating layer 427 functioning as a channel protection layer, source electrode layer 405a, and drain electrode It includes layer 405b. Furthermore, an insulating film 409 is formed covering the transistor 420.

[0130] The transistor 430 shown in Figure 11(C) is a bottom-gate type thin-film transistor, and is an insulating A gate electrode layer 401, a gate insulating layer 402, and a source electrode layer are placed on a substrate 400 having a surface. It includes 405a, a drain electrode layer 405b, and an oxide semiconductor layer 403. An insulating film 407 is provided that covers the sta 430 and is in contact with the oxide semiconductor layer 403. An insulating film 409 is further formed on the film 407.

[0131] In transistor 430, the gate insulating layer 402 is connected to the substrate 400 and the gate electrode layer 40 1 is provided in contact with the gate insulating layer 402, and the source electrode layer 405a and drain electrode layer 405b is provided in contact with it. And the gate insulating layer 402 and the source electrode layer 40 5a. An oxide semiconductor layer 403 is provided on the drain electrode layer 405b.

[0132] The transistor 440 shown in Figure 11(D) is a thin-film transistor with a top-gate structure. The transistor 440 is made of an insulating layer 437 and an oxide layer on a substrate 400 having an insulating surface. The oxide semiconductor layer 403, the source electrode layer 405a, the drain electrode layer 405b, and the gate insulating layer include the gate electrode layer 401, and wiring layers 436a and 436b are respectively provided in contact with the source electrode layer 405a and the drain electrode layer 405b and are electrically connected thereto.

[0133] In this embodiment, as described above, an oxide semiconductor layer 403 is used as the semiconductor layer. As the oxide semiconductor used for the oxide semiconductor layer 403, oxides of quaternary metals such as In-Sn-Ga-Zn-O, oxides of ternary metals such as In-Ga-Zn-O, In-Sn-Zn-O, In-Al-Zn-O, Sn-Ga-Zn-O, Al-Ga-Zn-O, Sn-Al-Zn-O, oxides of binary metals such as In-Zn-O, Sn-Zn-O, Al-Zn-O, Zn-Mg-O, Sn-Mg-O, In-Mg-O, In-O, Sn-O, Zn-O, etc. can be used. Further, the oxide semiconductor may contain SiO2. Here, for example, an In-Ga-Zn-O-based oxide semiconductor is an oxide containing at least In, Ga, and Zn, and there is no particular limitation on its composition ratio. It may also contain elements other than In, Ga, and Zn. Further, a thin film represented by the chemical formula InMO3(ZnO)m (m>0) can be used for the oxide semiconductor layer 403. Here, M represents one or more metal elements selected from Ga, Al, Mn, and Co. For example, as M, there are Ga, Ga and Al, Ga and Mn, or Ga and Co, etc.

[0134] The transistors 410, 420, 430, 440 using the oxide semiconductor layer 403 are in an off state

[0135] The current value in the state (off-current value) can be reduced. Therefore, the image data The holding time of electrical signals such as these can be extended, and the writing interval can also be set to be longer. This reduces the frequency of refresh operations, thus having the effect of suppressing power consumption. do.

[0136] Furthermore, transistors 410, 420, 430, and 440 using the oxide semiconductor layer 403 are, Because a relatively high field-effect mobility can be obtained, high-speed driving is possible. Therefore, liquid crystal display equipment By using this transistor in the pixel area, color separation can be suppressed, resulting in high-quality images. It can provide an image. Furthermore, the transistor can provide a drive circuit or image on the same substrate. Because the components can be manufactured separately, the number of parts in a liquid crystal display can be reduced. can.

[0137] There are no major restrictions on the substrates that can be used for the substrate 400 having an insulating surface, however Glass substrates such as borosilicate glass or aluminobrosilicate glass are used.

[0138] In bottom-gate transistors 410, 420, and 430, the insulating film that forms the base layer is used. A protective layer may be provided between the substrate and the gate electrode layer. The protective layer prevents the diffusion of impurity elements from the substrate. It has a stopping function, and is made of silicon nitride film, silicon oxide film, silicon nitride oxide film, or silicon oxide film. It can be formed by a laminated structure consisting of one or more films selected from silicon dioxide films.

[0139] The materials for the gate electrode layer 401 are molybdenum, titanium, chromium, tantalum, tungsten, Metal materials such as aluminum, copper, neodymium, scandium, or compounds mainly composed of these materials It can be formed using gold material, either as a single layer or in layers.

[0140] The gate insulating layer 402 is formed using plasma CVD or sputtering, etc. A layer, silicon nitride layer, silicon oxide nitride layer, silicon nitride oxide layer, aluminum oxide layer , aluminum nitride layer, aluminum oxide nitride layer, aluminum oxide nitride layer, or aluminum oxide The humium layer can be formed as a single layer or in multiple layers. For example, the first gate insulating layer and Then, a silicon nitride layer (SiN) with a thickness of 50 nm to 200 nm is formed by plasma CVD. A layer y(y>0) is formed, and a second gate insulating layer with a thickness of 5 nm is applied on the first gate insulating layer. By stacking silicon oxide layers (SiOx (x>0)) of 300 nm or less, the total film thickness is 20 The gate insulating layer is 0 nm thick.

[0141] Examples of conductive films used for the source electrode layer 405a and drain electrode layer 405b include Al , elements selected from Cr, Cu, Ta, Ti, Mo, W, or elements listed above as components A single alloy film or an alloy film combining the elements mentioned above can be used. In addition, Al, A high-melting-point metal layer such as Ti, Mo, or W is placed below, above, or on both sides of a metal layer such as Cu. A layered configuration is also possible. Furthermore, it prevents the formation of hillocks and whiskers in the Al film. By using Al material to which insulating elements (Si, Nd, Sc, etc.) are added, heat resistance is improved. It becomes possible to improve it.

[0142] Wiring layer 436a and wiring layer 43 connected to source electrode layer 405a and drain electrode layer 405b The conductive film, such as 6b, is made of the same material as the source electrode layer 405a and the drain electrode layer 405b. It can be used.

[0143] Furthermore, source electrode layer 405a, drain electrode layer 405b (wiring formed from the same layer) The conductive film (including the layer) may be formed from a conductive metal oxide. Examples of oxides include indium oxide (In2O3), tin oxide (SnO2), and zinc oxide (ZnO2). ), indium tin oxide alloy (In2O3-SnO2, abbreviated as ITO), zinc oxide alloy (In2O3-ZnO) or these metal oxide materials with silicon oxide Products containing corn can be used.

[0144] The insulating film 407 and insulating layers 427 and 437 are typically silicon oxide films and silicon oxide nitride films. Using an inorganic insulating film such as a film, an aluminum oxide film, or an aluminum oxide-nitride film. It is possible.

[0145] Insulating film 409 is silicon nitride film, aluminum nitride film, silicon nitride oxide film, silicon nitride oxide Inorganic insulating films, such as aluminum films, can be used.

[0146] Furthermore, a planarizing insulating film is formed on the insulating film 409 to reduce surface irregularities caused by the transistor. This may be done. As the planarizing insulating film, polyimide, acrylic, benzocyclobutene, etc. The following organic materials can be used. In addition to the above organic materials, low dielectric constant materials (low-k Materials such as these can be used. Furthermore, multiple insulating films formed from these materials can be stacked. A planar insulating film may be formed by doing so.

[0147] Thus, in this embodiment, a transistor including an oxide semiconductor layer is used. This allows us to provide more advanced liquid crystal display devices.

[0148] (Embodiment 6) This embodiment uses Figure 12 to illustrate an example of a transistor including an oxide semiconductor layer and a method for fabricating it. The following will be explained in detail: parts identical to or having similar functions to those in the above embodiment, and processes. This can be done in the same manner as in the above embodiment, and repeated explanations will be omitted. Also, the same part A detailed explanation will be omitted.

[0149] Figures 12(A) to 12(E) show examples of the cross-sectional structure of a transistor. The transistor 510 shown in Figure 12(E) is the same as the transistor 410 shown in Figure 11(A) This is a similar inverse staggered thin-film transistor with a bottom gate structure.

[0150] The oxide semiconductor used in the semiconductor layer of this embodiment is an oxide semiconductor in which hydrogen, which is an n-type impurity, is used. By removing impurities other than the main components of the oxide semiconductor and purifying it to a high degree, This results in an i-type (intrinsic) oxide semiconductor, or an oxide semiconductor that is very close to an i-type (intrinsic) one. This is the result. In other words, instead of adding impurities to make it i-type, it is the addition of hydrogen, water, and other impurities. By removing as much of the material as possible, a highly purified type i (intrinsic semiconductor) or something close to it can be produced. It is characterized by the following. Therefore, the oxide semiconductor layer of transistor 510 is made highly pure and It is an electrically i-type (intrinsic) oxide semiconductor layer.

[0151] Furthermore, highly purified oxide semiconductors contain very few carriers (close to zero), The ria concentration is less than 1 × 10¹⁴ / cm³, preferably less than 1 × 10¹² / cm³, and even more preferably The density is less than 1 × 10¹¹ / cm³.

[0152] Because there are very few carriers in the oxide semiconductor, the off-current of transistor 510 is low. This is possible. A lower off-current is preferable.

[0153] Specifically, the thin-film transistor having the oxide semiconductor layer described above has a channel width of 1 μm. The off-current density per unit is 10 aA / μm (1 × 10⁻¹⁷ A / μm) or less at room temperature. To make it so, and even less than 1 aA / μm (1 × 10⁻¹⁸ A / μm), and even less than 10 zA It is possible to reduce the level to less than / μm (1 × 10⁻²⁰ A / μm).

[0154] A transistor with an extremely small current value in the off state (off current value) is shown in the diagram of Embodiment 1. By using it as a transistor in the basic unit, refresh rate in the still image area This allows you to reduce the number of times you need to write to the work.

[0155] Furthermore, the transistor 510, which has the aforementioned oxide semiconductor layer, exhibits a temperature dependence of its on-current. It is hardly observed, and the off-current remains very low.

[0156] The transistor 510 is fabricated on the substrate 505 using Figures 12(A) to 12(E) below. I will explain the process.

[0157] First, a conductive film is formed on a substrate 505 having an insulating surface, and then a first photolithography is performed. The gate electrode layer 511 is formed by the process. The resist mask is made by the inkjet method. It may be formed. If the resist mask is formed by the inkjet method, a photomask is used. Therefore, manufacturing costs can be reduced.

[0158] The substrate 505 having an insulating surface is a substrate similar to the substrate 400 shown in Embodiment 5. This is possible. In this embodiment, a glass substrate is used as the substrate 505.

[0159] An insulating film that serves as the base layer may be provided between the substrate 505 and the gate electrode layer 511. It has the function of preventing the diffusion of impurity elements from the substrate 505, and silicon nitride film, silicon oxide One or more films selected from a silicon nitride film, silicon nitride film, or silicon oxide film. It can be formed by a laminated structure.

[0160] Furthermore, the material of the gate electrode layer 511 is molybdenum, titanium, tantalum, tungsten, and Metal materials such as luminium, copper, neodymium, scandium, or alloy materials with these as the main components. It can be formed using a material, either as a single layer or in layers.

[0161] Next, a gate insulating layer 507 is formed on the gate electrode layer 511. The gate insulating layer 507 is Using plasma CVD or sputtering methods, a silicon oxide layer and a silicon nitride layer are created. silicon oxide nitride layer, silicon oxide nitride layer, aluminum oxide layer, aluminum nitride layer , an aluminum oxide nitride layer, an aluminum oxide nitride layer, or a hafnium oxide layer as a single layer It can be formed by stacking layers.

[0162] The oxide semiconductor of this embodiment is an acid that has had impurities removed and has been type i or substantially type i. Oxide semiconductors are used. Such highly purified oxide semiconductors are suitable for interface levels and interface charges. Because it is extremely sensitive, the interface between the oxide semiconductor layer and the gate insulating layer is important. Therefore, the gate insulating layer that comes into contact with the highly purified oxide semiconductor requires high quality.

[0163] For example, high-density plasma CVD using μ-waves (e.g., frequency 2.45 GHz) is dense and It is preferable because it can form a high-quality insulating layer with high dielectric strength. The close contact between the high-quality gate insulating layer and the interface reduces the interface state and improves interface characteristics. This is because it can be done that way.

[0164] Of course, if it can form a good insulating layer as a gate insulating layer, sputtering Other film deposition methods such as plasma CVD can be applied. Furthermore, post-deposition heat treatment can be performed. Even if the insulating layer has modified film quality of the gate insulating layer and interface characteristics with the oxide semiconductor, Good. In any case, it is essential that the film quality as a gate insulating layer is good, and also that oxidation Any material that can reduce the interface state density with the semiconductor and form a good interface would be acceptable.

[0165] Furthermore, the gate insulating layer 507 and the oxide semiconductor film 530 contain as much hydrogen, hydroxyl groups, and moisture as possible. To prevent contamination, sputtering is used as a pretreatment for the deposition of the oxide semiconductor film 530. In the preheating chamber of the device, the substrate 505 on which the gate electrode layer 511 is formed, or the gate insulating layer 5 The substrate 505, on which layers 07 have been formed, is preheated to remove hydrogen, moisture, etc. adsorbed on the substrate 505. It is preferable to remove impurities and exhaust them. The exhaust means provided in the preheating chamber is cryogenic. A pump is preferred. Note that this preheating process can be omitted. The heat reaches the source electrode layer 515a and drain electrode layer 515b before the insulating layer 516 is formed. The same procedure may be performed on the formed substrate 505.

[0166] Next, a film thickness of 2 nm or more and 200 nm or less, preferably 5 nm or less, is applied to the gate insulating layer 507. An oxide semiconductor film 530 with a wavelength of 30 nm or less is formed (see Figure 12(A)).

[0167] Furthermore, before depositing the oxide semiconductor film 530 by sputtering, an argon gas is introduced. Reverse sputtering is performed to generate plasma by introducing the material, and it adheres to the surface of the gate insulating layer 507. It is preferable to remove the powdery material (also called particles or debris). Reverse sputtering is Without applying voltage to the target side, an RF power supply is used to apply voltage to the substrate side in an argon atmosphere. This method involves applying an argon atmosphere to form a plasma near the substrate and modify the surface. Nitrogen, helium, oxygen, etc., may be used instead of ambient air.

[0168] The oxide semiconductor used in the oxide semiconductor film 530 is an oxide of a quaternary metal as shown in Embodiment 5. These include oxides of ternary metals, oxides of binary metals, In-O systems, Sn-O systems, and Zn- Oxide semiconductors such as O-based semiconductors can be used. Furthermore, the above oxide semiconductor may contain SiO2. That is also acceptable. In this embodiment, the oxide semiconductor film 530 is an In-Ga-Zn-O based acid. The film is deposited using a chromium target by sputtering. Figure 12 shows a cross-sectional view at this stage. This corresponds to (A). Also, the oxide semiconductor film 530 is in a noble gas (typically argon) atmosphere. By sputtering under gas, in an oxygen atmosphere, or in a mixed atmosphere of noble gas and oxygen. It can be formed.

[0169] For example, a target for fabricating oxide semiconductor film 530 by sputtering is The composition ratio used is In2O3:Ga2O3:ZnO = 1:1:1 [molar ratio]. It is possible. Also, In2O3:Ga2O3:ZnO=1:1:2 [number of moles] It has a composition ratio of In2O3:Ga2O3:ZnO = 1:1:4 [molar ratio]. A target may be used. The packing density of the oxide semiconductor film deposition target is 90% or more. 0% or less, preferably 95% to 99.9%. High packing efficiency oxide semiconductor film deposition By using this method, the deposited oxide semiconductor film becomes a dense film.

[0170] The sputtering gas used when depositing the oxide semiconductor film 530 is hydrogen, water, hydroxyl group or hydrogen It is preferable to use a high-purity gas from which impurities such as monoxides have been removed.

[0171] The substrate is held in a film deposition chamber under reduced pressure, and the substrate temperature is kept between 100°C and 600°C. The temperature should be between 200°C and 400°C. By depositing the film while heating the substrate, The concentration of impurities in the deposited oxide semiconductor film can be reduced. Damage caused by rinsing is reduced. And, while removing residual moisture in the deposition chamber, hydrogen and moisture are removed. The removed sputtering gas is introduced, and the oxide semiconductor is placed on the substrate 505 using the target described above. A film 530 is deposited. To remove residual moisture in the deposition chamber, an adsorption-type vacuum pump is used, for example. For example, cryopumps, ion pumps, and titanium sublimation pumps are preferred. It seems so. Also, as an exhaust method, it was a turbo pump with a cold trap added. It is also possible. The deposition chamber, which is evacuated using a cryopump, contains, for example, hydrogen atoms and water (H2O). Compounds containing hydrogen atoms (more preferably compounds containing carbon atoms) are exhausted. Therefore, the concentration of impurities in the oxide semiconductor film deposited in the deposition chamber can be reduced.

[0172] An example of film deposition conditions is a distance of 100 mm between the substrate and the target, and a pressure of 0.6 Pa. The conditions applied are a DC power supply of 0.5kW and an oxygen atmosphere (oxygen flow rate ratio of 100%). It can be done. Furthermore, when using a pulsed DC power supply, powdery substances (particles) generated during film formation can be produced. This method is preferable because it reduces (also known as) the film thickness distribution and becomes more uniform.

[0173] Next, the oxide semiconductor film 530 is transformed into island-shaped oxide semiconductors by a second photolithography process. The material is processed into layers. Additionally, a resist mask is used to form island-shaped oxide semiconductor layers. It may also be formed by the jet method. If the resist mask is formed by the inkjet method, photomask Because no screws are used, manufacturing costs can be reduced.

[0174] Furthermore, when forming contact holes in the gate insulating layer 507, the process is carried out in an oxide semiconductor. This can be done simultaneously with the processing of film 530.

[0175] Note that the etching of the oxide semiconductor film 530 here can be done by dry etching or wet etching. Wetting is also acceptable, and both can be used. For example, wet etching of oxide semiconductor film 530 For etching, a solution of phosphoric acid, acetic acid, and nitric acid is used. This is possible. Alternatively, ITO07N (manufactured by Kanto Chemical Co., Ltd.) may be used.

[0176] Next, the oxide semiconductor layer is subjected to a first heat treatment. This first heat treatment causes the oxide semiconductor layer The conductive layer can be dehydrated or dehydrogenated. The temperature of the first heat treatment is 400°C. The temperature shall be 750°C or higher, or 400°C or higher, below the substrate's strain point. Here, the heat treatment equipment The substrate is introduced into an electric furnace, one of the furnaces, and the oxide semiconductor layer is subjected to a nitrogen atmosphere at 450°C. After a 1-hour heat treatment, water and water are removed from the oxide semiconductor layer without exposure to the atmosphere. This prevents the re-incorporation of the element and obtains the oxide semiconductor layer 531 (see Figure 12(B)).

[0177] Furthermore, the heat treatment device is not limited to electric furnaces, but also includes heat conduction or heat from heat-generating elements such as resistance heating elements. The device may include an apparatus that heats the object to be processed by radiation. For example, GRTA(Gas Rapid Thermal Anneal) equipment, LRTA (Lamp Rapid RTA (Rapid Thermal Angle) for Thermal Annealing devices, etc. A neal device can be used. The LRTA device uses halogen lamps and metal halide lamps. Lamps, xenon arc lamps, carbon arc lamps, high-pressure sodium lamps, high pressure A device that heats an object to be processed by radiation of light (electromagnetic waves) emitted from lamps such as mercury lamps. The GRTA device is a device that performs heat treatment using high-temperature gas. This involves using noble gases such as argon, or nitrogen, which do not react with the material being treated by heat treatment. An inert gas is used.

[0178] For example, as the first heat treatment, an inert gas heated to a high temperature of 650°C to 700°C The circuit board was moved inside and heated for several minutes, then moved again and heated to a high temperature in an inert solution. GRTA (Ground-Release Analysis) can be performed by releasing gas from the source.

[0179] In the first heat treatment, nitrogen or a noble gas such as helium, neon, or argon is used. It is preferable that it does not contain water, hydrogen, etc. Alternatively, nitrogen introduced into the heat treatment device, Alternatively, the purity of noble gases such as helium, neon, and argon must be 6N (99.9999%) or higher. Preferably 7N (99.99999%) or higher (i.e., impurity concentration of 1 ppm or less, preferably It is preferable to keep the concentration at 0.1 ppm or less.

[0180] Furthermore, after heating the oxide semiconductor layer in the first heat treatment, high-purity oxygen gas is added to the same furnace. A 10°C N2O gas or ultra-dry air (with a dew point of -40°C or lower, preferably -60°C or lower) is introduced. It may be added. It is preferable that the oxygen gas or N2O gas does not contain water, hydrogen, etc. Alternatively, the purity of the oxygen gas or N2O gas introduced into the heat treatment device is preferably 6N or higher. Alternatively, 7N or higher (i.e., the impurity concentration in oxygen gas or N2O gas should be 1 ppm or less). It is preferable to keep it below 0.1 ppm. Furthermore, the impurities were simultaneously reduced by the dehydration or dehydrogenation treatment process. By supplying oxygen, the oxide semiconductor layer is purified and electrically converted to type i (intrinsic). ru.

[0181] Furthermore, the first heat treatment of the oxide semiconductor layer is performed on the oxide before it is processed into an island-shaped oxide semiconductor layer. This can also be done on the semiconductor film 530. In that case, after the first heat treatment, the heating device is used The substrate is removed, and the photolithography process is performed.

[0182] Furthermore, the first heat treatment can also be performed after oxide semiconductor layer deposition, in addition to the above. After stacking the source electrode layer and the drain electrode layer on top of the layer, or the source electrode layer and the drain This can be done either after forming an insulating layer on the rain electrode layer.

[0183] Furthermore, when forming contact holes in the gate insulating layer 507, the process is carried out in an oxide semiconductor. This can be done before or after the first heat treatment is performed on the film 530.

[0184] Furthermore, by depositing the oxide semiconductor layer in two stages and performing heat treatment in two stages, the substrate Regardless of the material of the component, such as oxides, nitrides, or metals, the crystalline region (single crystal region) with a thick film thickness is a single crystal region. Even if an oxide semiconductor layer is formed having a crystalline region (i.e., a c-axis oriented region perpendicular to the film surface), Good. For example, a first oxide semiconductor film of 3 nm to 15 nm is formed, and nitrogen, oxygen, In an atmosphere of noble gas or dry air, at a temperature of 450°C to 850°C, preferably 550°C or lower. A first heat treatment is performed at a temperature of 750°C or lower, and a crystalline region (including plate-like crystals) is formed in the region including the surface. A first oxide semiconductor film having the following characteristics is formed. Then, a second oxide semiconductor film thicker than the first oxide semiconductor film is formed. Form an oxide semiconductor film of type 2, and heat at a temperature of 450°C to 850°C, preferably 600°C to 70°C. A second heat treatment is performed at a temperature below 0°C, and the first oxide semiconductor film is used as a seed for crystal growth, and upward Crystal growth is performed to crystallize the entire second oxide semiconductor film, resulting in a thick crystalline region. An oxide semiconductor layer having a region may be formed.

[0185] Next, a source electrode layer and a drain are placed on the gate insulating layer 507 and the oxide semiconductor layer 531. A conductive film is formed to form the electrode layer (including wiring formed from the same layer). Source electrode As the conductive film used for the layer and the drain electrode layer, the source electrode layer 4 shown in Embodiment 5 is used. The material used for 05a and the drain electrode layer 405b can be applied.

[0186] A third photolithography step forms a resist mask on the conductive film, and selectively extracts the residue. After performing ching to form the source electrode layer 515a and the drain electrode layer 515b, a resist is applied. Remove the mask (see Figure 12(C)).

[0187] For exposure during resist mask formation in the third photolithography process, ultraviolet light and KrF light are used. It is preferable to use a laser or ArF laser. Adjacent source electrodes on the oxide semiconductor layer 531 The gap width between the lower end of the layer and the lower end of the drain electrode layer determines the transistor that is later formed. The channel length L is determined. Note that if exposure is performed with a channel length L of less than 25 nm, Extreme ultraviolet light (Ultraviolet) is a type of ultraviolet light with extremely short wavelengths ranging from a few nanometers to tens of nanometers. Using iolet, exposure during resist mask formation in the third photolithography step It is recommended to do so. Exposure with ultra-ultraviolet light has high resolution and a large depth of field. Therefore, later formation It is also possible to set the channel length L of the transistor to between 10 nm and 1000 nm. Yes, it allows for faster circuit operation speeds, and because the off-current value is extremely small, it consumes low power. It can also be transformed.

[0188] Furthermore, in order to reduce the number of photomasks and processes used in the photolithography process, The resist mask formed by a multi-tone mask, which is an exposure mask where the light has multiple intensities, is formed by the light. The etching process may be performed using a mask. A resist mask formed using a multi-gradation mask. The ske will have a shape with multiple film thicknesses, and its shape can be further deformed by etching. Because it can do this, it can be used in multiple etching processes that process different patterns. Therefore, a single multi-tone mask can accommodate at least two different patterns. This allows for the formation of a resist mask. Therefore, the number of exposure masks can be reduced. Furthermore, the corresponding photolithography process can also be reduced, thus simplifying the overall process.

[0189] Furthermore, during the etching of the conductive film, the oxide semiconductor layer 531 is etched and fragmented. It is desirable to optimize the etching conditions to avoid this. However, only conductive films To etch the oxide semiconductor layer 531 without etching it at all is to obtain the condition that It is difficult, and during the etching of the conductive film, only a portion of the oxide semiconductor layer 531 is etched. It can also form an oxide semiconductor layer with grooves (recesses).

[0190] In this embodiment, a Ti film is used as the conductive film, and the oxide semiconductor layer 531 is made of In-Ga- Since a Zn-O-based oxide semiconductor was used, ammonia hydrogen peroxide (A) was used as the etchant for the conductive film. Use a mixture of water, hydrogen peroxide, and water.

[0191] Next, plasma treatment is performed using a gas such as N2O, N2, or Ar, and the exposed material is then... Adsorbed water and other substances attached to the surface of the oxide semiconductor layer may be removed. In this case, an insulating layer 5 becomes a protective insulating film that contacts a portion of the oxide semiconductor layer without being exposed to the atmosphere. Forms 16.

[0192] The insulating layer 516 has a thickness of at least 1 nm, and is formed by sputtering or other methods. 6 can be formed using an appropriate method that prevents the introduction of impurities such as water and hydrogen. If hydrogen is present in 516, the hydrogen may penetrate the oxide semiconductor layer, or the hydrogen may enter the oxide semiconductor layer. Oxygen is extracted from the body layer, causing the back channel of the oxide semiconductor layer to become less resistive (n-type). This can lead to the formation of parasitic channels. Therefore, the insulating layer 516 should be as low as possible. To ensure that the resulting film is hydrogen-free, it is important to avoid using hydrogen in the film formation method.

[0193] In this embodiment, a silicon oxide film with a thickness of 200 nm is sputtered as the insulating layer 516. The film is deposited using the 3D method. The substrate temperature during film deposition should be between room temperature and 300°C. The application method is set to 100°C. For silicon oxide film deposition by sputtering, a rare gas Under an atmosphere (typically argon), an oxygen atmosphere, or a mixed atmosphere of a noble gas and oxygen It can be done in a place. Also, silicon oxide target or silico A silicon target can be used. For example, a silicon target can be used to include oxygen. Silicon oxide can be formed by sputtering under atmospheric conditions. The insulating layer 516 formed in contact with the layer does not contain impurities such as moisture, hydrogen ions, and OH-. Instead, an inorganic insulating film is used to block these from entering from the outside, typically an oxide film. Silicon oxide film, silicon oxide nitride film, aluminum oxide film, or aluminum oxide nitride film You can use these.

[0194] Similar to the deposition of the oxide semiconductor film 530, residual moisture in the deposition chamber of the insulating layer 516 is removed. For this purpose, it is preferable to use an adsorption-type vacuum pump (such as a cryopump). The concentration of impurities in the insulating layer 516 deposited in the deposition chamber, which is evacuated using an op-pump, is reduced. Yes, it is possible. Furthermore, as an exhaust means for removing residual moisture in the film deposition chamber of the insulating layer 516, A turbopump with a cold trap added may also be used.

[0195] The sputtering gas used when forming the insulating layer 516 is hydrogen, water, hydroxyl groups, or hydrides. It is preferable to use a high-purity gas from which impurities have been removed.

[0196] Next, a second heat treatment (preferably 2) is performed under an inert gas atmosphere or an oxygen gas atmosphere. Perform the procedure at temperatures between 0°C and 400°C (for example, between 250°C and 350°C). For example, under a nitrogen atmosphere. A second heat treatment is performed at 250°C for 1 hour under gas pressure. After the second heat treatment, the oxide semiconductor A portion of the body layer (channel-forming region) is heated while in contact with the insulating layer 516.

[0197] Through the above steps, the oxide semiconductor film is subjected to a first heat treatment to release hydrogen. Impurities such as water, hydroxyl groups, or hydrides (also called hydrogen compounds) are removed from the oxide semiconductor layer. To graphically remove impurities and simultaneously supply oxygen that is reduced by the impurity removal process. This is possible. Therefore, the oxide semiconductor layer becomes highly purified and electrically i-type (intrinsic).

[0198] The transistor 510 is formed through the above process (see Figure 12(D)).

[0199] Furthermore, if a silicon oxide layer containing many defects is used in the oxide insulating layer, after the silicon oxide layer is formed... By heat treatment, hydrogen, water, hydroxyl groups or hydrides contained in the oxide semiconductor layer are removed. The impurities are diffused into the oxide insulating layer, and the impurities contained in the oxide semiconductor layer are further reduced. It produces the effect of [this].

[0200] A protective insulating layer 506 may be formed on the insulating layer 516. For example, RF sputtering A silicon nitride film is formed using the sputtering method. RF sputtering is suitable for mass production because it offers good mass production capabilities. This is a preferred method for forming a protective insulating layer. The protective insulating layer 506 does not contain impurities such as moisture. Using an inorganic insulating film that blocks these from entering from the outside, a silicon nitride film, nitrogen Aluminum oxide film and the like can be used. In this embodiment, the protective insulating layer 506 is It is formed using a silicon nitride film (see Figure 12(E)).

[0201] In this embodiment, the protective insulating layer 506 is made of the substrate 505 formed up to the insulating layer 516. It contains high-purity nitrogen that has been heated to a temperature between 100°C and 400°C, from which hydrogen and water have been removed. A silicon nitride film is deposited using a silicon semiconductor target after introducing a sputtering gas. In this case as well, similar to the insulating layer 516, the residual moisture in the processing chamber is removed while protecting the insulation It is preferable to form a marginal layer 506.

[0202] After the formation of the protective insulating layer 506, further heating in an atmospheric atmosphere at a temperature between 100°C and 200°C for 1 hour or more. Heat treatment may be performed for 30 hours or less. This heat treatment is performed while maintaining a constant heating temperature. It may be heated, or the temperature may be raised from room temperature to a heating temperature of 100°C to 200°C, and the heating temperature You may repeat the process of lowering the temperature from a certain degree to room temperature multiple times.

[0203] Thus, a trace containing a highly purified oxide semiconductor layer fabricated using this embodiment By using an inverter, the current value in the off state (off current value) can be made lower. This allows for longer retention times for electrical signals such as image data. Furthermore, the write interval can be set to be longer. Therefore, the frequency of refresh operations can be reduced. This allows for a reduction in power consumption.

[0204] Furthermore, transistors containing a highly purified oxide semiconductor layer can achieve high field-effect mobility. Therefore, high-speed driving is possible. Thus, the transistor is used in the pixel section of a liquid crystal display device. This allows for the provision of high-quality images. Furthermore, the transistor is on the same substrate. Because it can be manufactured by separately creating the drive circuit section or the pixel section on top, the liquid crystal display device The number of items can be reduced.

[0205] This embodiment can be implemented in appropriate combination with other embodiments.

[0206] (Embodiment 7) In this embodiment, the amount of reflected light and transmitted light per pixel of the semi-transmissive liquid crystal display device is improved. The pixel configuration will be explained using Figures 14, 15, and 16.

[0207] Figure 14 is a diagram illustrating the planar configuration of pixels shown in this embodiment. Figure 15 is a diagram. Sectional structure of parts S1-S2, T1-T2, and U1-U2 shown by the dashed line in 14 This shows the result. The pixels described in this embodiment are placed on the substrate 800 as transparent as pixel electrodes. Electrode 823 and reflective electrode 825 are stacked with an insulating layer 824 in between.

[0208] The transparent electrode 823 is provided on the insulating film 827, insulating film 828, and organic resin film 822. Connected to the drain electrode 857 of transistor 851 via contact hole 855 The drain electrode 857 is superimposed on the capacitive wiring 853 via the gate insulating layer, and retains capacitance. It constitutes 871 (see Figure 15(A)).

[0209] Furthermore, the gate electrode 858 of transistor 851 is connected to wiring 852, source Electrode 856 is connected to wiring 854. Transistor 851 is in another embodiment. The transistor described can be used (see Figure 14).

[0210] The reflective electrode 825 is provided on the insulating film 827, insulating film 828, and organic resin film 822. Connected to the drain electrode 867 of transistor 861 via contact hole 865 (See Figure 15(E)). The drain electrode 867 is connected to the capacitive wiring 86 via the gate insulating layer. It is superimposed on 3 to form a holding capacity of 872.

[0211] The gate electrode 868 of transistor 861 is connected to wiring 862, and the source electrode 8 66 is connected to wiring 864. Transistor 861 is described in other embodiments. A transistor can be used (see Figure 14).

[0212] By reflecting ambient light with the reflective electrode 825, the pixel electrode of the reflective liquid crystal display device is converted to a pixel electrode. It can be made to function as such. The reflective electrode 825 is provided with multiple openings 826. The reflective electrode 825 is not present in the opening 826, and the structure 820 and the transparent electrode 823 protrude. It is being emitted (see Figure 15(B)). The backlight is transmitted through the opening 826. This allows the pixel electrodes to function as pixel electrodes in a transmissive liquid crystal display device.

[0213] In the semi-transmissive liquid crystal display device shown in this embodiment, the reflective electrode 825 and the transparent electrode 823 are insulated. It is electrically isolated by layer 824. Also, the potential applied to the transparent electrode 823 is a transistor Since it is controlled by 851 and the potential applied to the reflecting electrode 825 can be controlled by transistor 861, The potentials of the reflective electrode 825 and the transparent electrode 823 can be controlled independently. Therefore, when a semi-transmissive liquid crystal display device is functioning as a transmissive type, on the reflective electrode 825 The LCD display can be made to show black.

[0214] Furthermore, Figure 16 is a cross-sectional view showing a different example from Figure 15(B), and at the opening 826 In one embodiment of the present invention, the structure 820 and the transparent electrode 823 are not protruding. Yes. In Figure 15(B), the backlight emission port 841 and the opening 826 are approximately the same size. In contrast, Figure 16 shows the size of the backlight emission port 841 and the opening 826. The size is different, and the distance from the backlight incident light opening 842 is also different. Therefore, compared to Figure 16... In comparison, Figure 15(B) allows for a greater amount of transmitted light, and can be said to have a preferable cross-sectional shape. ru.

[0215] In the opening 826, the structure 820 is formed superimposed on the opening 826. Figure 15(B Figure 14 shows a cross-sectional view of the T1-T2 section, illustrating the configuration of the pixel electrode and structure 820. Figure 15(C) is a magnified view of part 880, and Figure 15(D) is a magnified view of part 881. Enlarged view.

[0216] The reflected light 832 shows the ambient light reflected by the reflective electrode 825. The organic resin film 822 is The upper surface has an uneven, curved surface. The curved surface with its uneven shape is reflected in the reflective electrode 825. This increases the area of ​​the reflective surface and reduces reflections of elements other than the displayed image. The visibility of the displayed image can be improved. Reflective electrode 82 has a curved surface in its cross-sectional shape. From the most bent point of 5, the angle θR between the two opposing inclined surfaces is greater than 90°. Preferably, the angle should be between 100° and 120° (see Figure 15(D)).

[0217] Structure 820 has a backlight emission port 841 on the side of the opening 826, and backlight ( The side (not shown) has a backlight incident light opening 842. Also, the upper part of the structure 820 is It is located above the surface of the reflecting electrode 825 and has a shape that protrudes above the upper end of the reflecting electrode, The distance H between the upper end of the structure 820 and the upper end of the reflecting electrode is 0.1 μm or more and 3 μm or less. Preferably, it is 0.3 μm or more and 2 μm or less. Also, the area of ​​the backlight emission port 841. The area of ​​the backlight incident light opening 842 is larger than that of the side of the structure 820. The surface (surfaces other than the backlight emission port 841 and the backlight incident port 842) has a reflective layer. Structure 821 is formed. Structure 820 is silicon oxide, silicon nitride, silicon oxynitride Translucent materials such as condensing can be used. The reflective layer 821 is made of aluminum. Materials with high light reflectivity, such as aluminum (Al) and silver (Ag), can be used.

[0218] The transmitted light 831 emitted from the backlight passes through the backlight incident light opening 842 and forms a structure The light enters the body 820. A portion of the transmitted light 831 is then directed to the backlight exit port 84. The light is emitted from 1, but some of it is directed towards the backlight emission port 841 by the reflective layer 821. The light is reflected, and some of it is reflected again, returning to the backlight incident light opening 842.

[0219] At this time, the light passes through the backlight emission port 841 and backlight incident port 842 of the structure 820. Looking at the cross-sectional shape of the structure 820, the left and right opposing sides are inclined surfaces. The angle θT formed by each side is less than 90°, preferably between 10° and 60°. Then, the transmitted light 831 that enters from the backlight entrance port 842 is efficiently emitted as backlight. It can be directed to the light port 841 (see Figure 15(C)).

[0220] For example, in one pixel, the area of ​​the pixel electrode is set to 100%, and the reflective electrode is set to The electrode area capable of performing functions is SR, and the electrode area that functions as a permeable electrode (area of ​​the opening 826) is ST. In that case, the electrode area that functions as a reflective electrode in a conventional semi-transparent liquid crystal display device is... The combined area of ​​SR and the electrode area ST, which functions as a transmission electrode, equals 100% of the pixel electrode area. Corresponding. In the semi-transmissive liquid crystal display device having the pixel configuration shown in this embodiment, the transmitted electrode The electrode area ST, which functions as such, corresponds to the area of ​​the backlight incident light aperture 842, The area ST of section 826 can be increased. Also, the electrode area that functions as a permeable electrode can be increased. Since ST corresponds to the area of ​​the backlight incident light opening 842, the brightness of the backlight is increased. This allows for an improvement in transmitted light intensity without any additional processing. This enables the electrode to function as a reflective electrode. The total area of ​​the area SR and the electrode area ST, which functions as a permeable electrode, must be 100% or more. Yes, it is possible. In other words, the apparent area of ​​the pixel electrodes can be made to more than 100%.

[0221] By using this embodiment, a brighter, higher-quality semi-transparent display can be achieved without increasing power consumption. A liquid crystal display device can be obtained.

[0222] (Embodiment 8) In this embodiment, the electronic device equipped with the liquid crystal display device described in the above embodiment Let me explain with an example.

[0223] Figure 13(A) shows an e-book, consisting of a casing 9630 and a display unit 963 1. It may have an operation key 9632, a solar cell 9633, and a charge / discharge control circuit 9634. The e-book shown in Figure 13(A) contains various types of information (still images, videos, text images, etc.). Functions to display, such as a calendar, date or time, on the display unit, and display on the display unit Functions to manipulate or edit the information, and control processing by various software (programs). It can have functions such as controlling the system. Note that in Figure 13(A), the charge / discharge control circuit 9634 One example is the battery 9635, and the DC-DC converter (hereinafter abbreviated as converter 9636). This describes a configuration that has the following characteristics:

[0224] By using the configuration shown in Figure 13(A), the display unit 9631 is a semi-transmissive liquid crystal display unit. When using the device, it is expected to be used in relatively bright conditions, and power generation by solar cell 9633 is also expected. Furthermore, it is suitable because it allows for efficient charging with the battery 9635. The battery 9633 efficiently charges the battery 9635 on the front and back surfaces of the housing 9630. This configuration is preferable. Note that the battery 9635 is lithium Using an on-cell battery offers advantages such as miniaturization.

[0225] Furthermore, the configuration and operation of the charge / discharge control circuit 9634 shown in Figure 13(A) are shown in Figure 13(B). The block diagram is shown and explained below. Figure 13(B) shows the solar cell 9633 and the battery 963 5. Converter 9636, Converter 9637, Switches SW1 to SW3, Display unit 96 31 indicates battery 9635, converter 9636, converter 963 7. Switches SW1 to SW3 correspond to the charge / discharge control circuit 9634.

[0226] First, let's explain an example of operation when electricity is generated by the solar cell 9633 using ambient light. The electricity generated by the solar panels is converted to a voltage suitable for charging the 9635 battery. The voltage is boosted or lowered at 9636. Then, the solar cell 9 controls the operation of the display unit 9631. When power from 633 is used, switch SW1 is turned ON, and converter 9637 The voltage will be increased or decreased to the voltage required for the display unit 9631. If you do not want the display to appear, turn SW1 off and SW2 on and use battery 9635 The configuration should be such that it charges the device.

[0227] Next, we will explain an example of operation when the solar cell 9633 does not generate electricity due to ambient light. The power stored in battery 9635 is converted by turning on switch SW3. The voltage is increased or decreased by the 9637. Then, the battery operates in accordance with the operation of the display unit 9631. The power will be supplied from the Lee 9635.

[0228] Note that the solar cell 9633 was shown as an example of a charging method, but other means of charging are also available. The configuration may also include charging the Terry 9635. Alternatively, it may be done in combination with other charging methods. It can also be used as a composition.

[0229] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments. That is the case. [Explanation of Symbols]

[0230] 100 LCD display device 101 Image signal source 102 A / D conversion circuit 110 Image Processing Circuit 111 Memory circuit 112 Comparison circuit 113 Display control circuit 114 Field Sequential Signal Generation Circuit 115 Selection Circuit 120 Display Panel 121 Drive Circuit 122 pixel section 123 pixel section 123a subpixel 123b subpixel 125a polarizing plate 125b Polarizing plate 126 FPC 130 Backlight section 131 Backlight control circuit 132 Backlight 133 Light-emitting element 133R LED 133G LED 133B LED 134 Diffuser 135 light 139 Outdoor light 140 Analog image signals 141 Digital image signals 142 LC image signal 143 Backlight signal 151 pixel section 152 First scan line 153 First signal line 154 Second scan line 155 Second signal line 156 pixels 157 First scan line drive circuit 158 First signal line drive circuit 159 Second scan line drive circuit 160 Second signal line drive circuit 161 Transparent electrode section 162 Reflective electrode section 163 Pixel Transistors 164 liquid crystal elements 165 Capacitive elements 166-pixel transistor 167 Liquid crystal elements 168 Capacitive elements 169 Common electrode 170 Capacity Line 190 LCD Display Module 301 Video display period 302 Still image display period 303 Still image writing period 304 Still image retention period 311 Light-emitting element 400 circuit boards 401 Guard Layer 402 Gate Insulation Layer 403 Oxide semiconductor layer 405a Source electrode layer 405b Drain electrode layer 407 Insulating film 409 Insulating film 410 transistors 413 Interlaminar 420 transistors 427 Insulating layer 430 transistors 436a Wiring layer 436b wiring layer 437 Insulating layer 440 transistors 441 circuit board 442 circuit boards 444 liquid crystal layers 448 Common electrode layer 460a alignment film 460b oriented film 480 Insulating layer 482 Insulating layer 498 Reflection area 499 Transparent area 505 circuit board 506 Protective insulating layer 507 Gate Insulation Layer 510 transistors 511 Gridgate Layer 515a Source electrode layer 515b Drain electrode layer 516 Insulating layer 530 Oxide semiconductor film 531 Oxide semiconductor layer 550 transistors 551 Binding circuit layer 553 Semiconductor layer 555a Source electrode layer or drain electrode layer 555b Source electrode layer or drain electrode layer 558 Capacitive wiring layer 560 transistors 563 Semiconductor layer 565a Source electrode layer or drain electrode layer 565b Source electrode layer or drain electrode layer 571 Insulating film 576 Transparent electrode layer 577 Reflective electrode layer 579 Conductive layer 580 wiring layer 800 circuit boards 820 Structure 821 Reflective layer 822 Organic resin film 823 Transparent electrode 824 Insulating layer 825 Reflective electrode 826 Opening 827 Insulating film 828 Insulating Film 831 Transmitted light 832 Reflected light 841 Backlight output port 842 Backlight Incident Light Port 851 Transistors 852 Wiring 853 Capacitance wiring 854 Wiring 855 Contact Hole 856 Source electrode 857 Drain electrode 858 Gate 861 Transistors 862 Wiring 863 Capacitance wiring 864 Wiring 865 Contact Hole 866 Source Electrode 867 Drain electrode 868 Entry gate 871 Holding capacity 872 holding capacity 880 parts 881 parts 9630 cabinet 9631 Display section 9632 Operation Keys 9633 Solar Cell 9634 Charge / Discharge Control Circuit 9635 Battery 9636 converter 9637 Converter

Claims

1. It has a backlight and a display panel, The display panel includes a first pixel electrode, a second pixel electrode, and a structure. The first pixel electrode described above has the function of transmitting light, The second pixel electrode is a liquid crystal display device having the function of reflecting light, The first pixel electrode and the second pixel electrode have overlapping regions separated by an insulating layer. The first pixel electrode has a region located on the structure, The insulating layer has a region located on the first pixel electrode, The second pixel electrode has a region located on the insulating layer, The second pixel electrode described above has a plurality of apertures, One of the plurality of openings has a region that overlaps with the structure, In one of the plurality of openings, the structure has a region that protrudes from the upper surface of the second pixel electrode, The backlight is located below the first pixel electrode in the liquid crystal display device.

2. It has a backlight and a display panel, The display panel includes a first pixel electrode, a second pixel electrode, a structure, and a transistor. The first pixel electrode described above has the function of transmitting light, The second pixel electrode is a liquid crystal display device having the function of reflecting light, The first pixel electrode and the second pixel electrode have overlapping regions separated by an insulating layer. The first pixel electrode has a region located on the structure, The insulating layer has a region located on the first pixel electrode, The second pixel electrode has a region located on the insulating layer, The second pixel electrode described above has a plurality of apertures, One of the plurality of openings has a region that overlaps with the structure, In one of the plurality of openings, the structure has a region that protrudes from the upper surface of the second pixel electrode, The backlight is positioned below the first pixel electrode, The second pixel electrode is electrically connected to either the source or the drain of the transistor. The transistor has an oxide semiconductor in the channel formation region. The aforementioned oxide semiconductor is In-O, and the liquid crystal display device.

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