JP2004004938A - Liquid crystal display and electronic equipment - Google Patents

Abstract

An object of the present invention is to provide a transflective liquid crystal display device capable of obtaining a bright, high-contrast display with a wide viewing angle.
A liquid crystal display device according to the present invention employs a vertical alignment mode using a liquid crystal layer 50 whose initial alignment state is a vertical alignment, and a transmissive display region T surrounds a reflective display region R in one dot. And an insulating film 21 for making the layer thickness of the liquid crystal layer 50 in the reflective display region R smaller than the layer thickness of the liquid crystal layer 50 in the transmissive display region T corresponds to the reflective display region R at the center of the dot. Is provided in the region where
[Selection diagram] Fig. 3

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a technique capable of obtaining a display with a high contrast and a wide viewing angle in a transflective liquid crystal display device that performs display in both a reflection mode and a transmission mode. .
[0002]
[Prior art]
Reflection type liquid crystal display devices have low power consumption because they do not have a light source such as a backlight, and have been widely used in various portable electronic devices. However, since the reflective liquid crystal display device performs display using external light such as sunlight or illumination light, there is a problem that it is difficult to visually recognize the display in a dark place. Therefore, there has been proposed a liquid crystal display device in which external light is used in a bright place similarly to a normal reflection type liquid crystal display device, and in a dark place, the display can be visually recognized by an internal light source such as a backlight. In other words, this liquid crystal display device employs a display system having both a reflection type and a transmission type. By switching between the reflection mode and the transmission mode according to the surrounding brightness, power consumption is reduced. It is possible to provide a clear display even when the surroundings are dark while reducing the amount of light. Hereinafter, in this specification, this type of liquid crystal display device is referred to as a “semi-transmissive reflective liquid crystal display device”.
[0003]
Such a transflective liquid crystal display device has a structure in which a liquid crystal layer is sandwiched between an upper substrate and a lower substrate, and has a reflective film in which a window for light transmission is formed in a metal film such as aluminum. A liquid crystal display device has been proposed in which a film is provided on the inner surface of a lower substrate, and the reflective film functions as a transflective film. In this case, in the reflection mode, external light incident from the upper substrate side passes through the liquid crystal layer, is reflected by the reflection film on the inner surface of the lower substrate, passes through the liquid crystal layer again, and is emitted from the upper substrate side, contributing to display. I do. On the other hand, in the transmission mode, light from the backlight incident from the lower substrate side passes through the liquid crystal layer from the window of the reflection film, and then exits from the upper substrate side to contribute to display. Therefore, of the reflective film forming region, the region where the window is formed is the transmissive display region, and the other regions are the reflective display regions.
[0004]
By the way, the alignment mode of the liquid crystal includes a twisted nematic (hereinafter abbreviated as TN) mode in which liquid crystal molecules are aligned in a direction substantially parallel to the substrate surface and twisted in a direction perpendicular to the substrate when no voltage is applied. And a vertical alignment mode in which liquid crystal molecules are vertically aligned. Conventionally, the TN mode has been the mainstream in terms of reliability and the like, but since the vertical alignment mode has some excellent characteristics, a vertical alignment mode liquid crystal device has been attracting attention.
[0005]
For example, in the vertical alignment mode, a state in which liquid crystal molecules are arranged perpendicular to the substrate surface (no optical retardation as viewed from the normal direction) is used as a black display, so that the quality of the black display is good and high. Contrast is obtained. In a vertical alignment type LCD having excellent front contrast, a viewing angle range in which a constant contrast can be obtained is wider than that in a horizontal alignment mode TN liquid crystal. Furthermore, if an orientation division (multi-domain) technique for dividing the orientation direction of the liquid crystal in the pixel is adopted, an extremely wide viewing angle can be obtained.
[0006]
In the transflective liquid crystal display device having the above-described configuration, for example, if the thickness of the liquid crystal layer is d, the anisotropy of the refractive index of the liquid crystal is Δn, and the retardation of the liquid crystal represented by the integrated value is Δn · d, the reflective display is performed. The retardation of the liquid crystal in the region is represented by 2 × Δn · d because the incident light reaches the observer after passing twice through the liquid crystal layer. On the other hand, the retardation of the liquid crystal in the transmissive display area is 1 × Δn · d because the light from the backlight passes through the liquid crystal layer only once.
[0007]
As described above, when the alignment of the liquid crystal molecules in the liquid crystal layer is controlled while the reflective display area and the transmissive display area have different retardation values, conventionally, an electric field is applied to the liquid crystal with the same driving voltage in each display mode. The voltage is applied to control the orientation. In this case, high-contrast display cannot be obtained by aligning the liquid crystal having different retardation states in the liquid crystal in different display modes, in other words, in the transmissive display area and the reflective display area with the same driving voltage. There was a problem. In order to solve this problem, a liquid crystal display device having a structure in which the thickness of a liquid crystal layer is changed between a transmission type display region and a reflection type display region has been proposed (for example, see Patent Document 1).
[0008]
[Patent Document 1]
JP-A-11-242226
[0009]
[Problems to be solved by the invention]
As described above, the use of the vertical alignment mode is one technique for achieving high contrast, and there is also a demand for configuring a liquid crystal display device by combining a vertical alignment mode with a transflective liquid crystal display device. However, there are problems to be solved, such as a problem of a decrease in contrast due to a retardation difference in both the reflection and transmission display modes, a problem of alignment control in the vertical alignment mode, and a problem of alignment division. It is.
[0010]
The present invention has been made in order to solve the above problems, and in a transflective liquid crystal display device, there is provided a liquid crystal display device capable of obtaining a bright, high-contrast, and display with a wide viewing angle. The purpose is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a liquid crystal display device of the present invention has a liquid crystal layer sandwiched between a pair of substrates, and has a transmissive display area for performing transmissive display in one dot area and a reflective display for performing reflective display. A region and a liquid crystal display device provided individually, wherein the liquid crystal layer is a liquid crystal layer in which an initial alignment state exhibits vertical alignment, and a liquid crystal layer of at least one of the pair of substrates and the liquid crystal layer. An insulating film that varies the thickness of the liquid crystal layer between the reflective display area and the transmissive display area depending on the film thickness is provided at least in the reflective display area.
[0012]
The liquid crystal display device of the present invention is obtained by combining a transflective liquid crystal display device with a liquid crystal in a vertical alignment mode. In recent years, in a transflective liquid crystal display device, in order to solve the problem of a decrease in contrast due to a retardation difference in both the reflective and transmissive display modes, for example, an insulating film having a predetermined thickness in a reflective display region on a lower substrate Is formed so as to protrude toward the liquid crystal layer side, so that the thickness of the liquid crystal layer is changed between the reflective display area and the transmissive display area. The present applicant has already applied for many inventions of this type of liquid crystal display device. According to this configuration, the thickness of the liquid crystal layer in the reflective display area can be made smaller than the thickness of the liquid crystal layer in the transmissive display area due to the presence of the insulating film, so that the retardation in the reflective display area and the retardation in the transmissive display area are sufficiently increased. , Or approximately equal, thereby improving the contrast.
[0013]
Therefore, the present inventors have found that by combining a liquid crystal display device having the above-described insulating film with a liquid crystal layer of a vertical alignment mode, the alignment direction of the liquid crystal in the vertical alignment mode when an electric field is applied can be controlled. In other words, when the vertical alignment mode is adopted, a negative type liquid crystal is generally used. However, the liquid crystal molecules standing vertically to the substrate surface in the initial alignment state are defeated by applying an electric field. Unless devised (unless a pre-tilt is provided), the direction in which the liquid crystal molecules fall cannot be controlled, and disorder in the alignment (disclination) occurs, causing display defects such as light leakage and deteriorating the display quality. . Therefore, in adopting the vertical alignment mode, control of the alignment direction of liquid crystal molecules when an electric field is applied is an important factor. Therefore, in a liquid crystal display device having the above-described insulating film, the insulating film protrudes toward the liquid crystal layer, so that the insulating film becomes a projection, so that the liquid crystal molecules exhibit vertical alignment in an initial state. The projection has a pretilt according to the shape of the projection. By this action, the orientation direction of the liquid crystal molecules when an electric field is applied can be controlled, so that a display with high contrast can be realized without display defects such as light leakage.
[0014]
That is, according to the configuration of the present invention, by providing the transflective liquid crystal display device of the vertical alignment mode with the insulating film, both the reflection and transmissive problems, which have been fundamental problems of the transflective liquid crystal display device in the past, have been achieved. It is possible to solve the problem of the decrease in contrast due to the retardation difference in the display mode, and at the same time, it is possible to suppress the display failure due to the inability to control the alignment direction of liquid crystal molecules in the vertical alignment mode. As a result, both the advantage of the vertical alignment mode and the advantage of the transflective type can be utilized, and a liquid crystal display device with excellent display quality can be realized.
[0015]
The arrangement of the transmissive display area and the reflective display area in one dot area can be arbitrarily set. In particular, the transmissive display area is provided so as to surround the periphery of the reflective display area, and the insulating film is formed at the center of the dot. Is preferably provided in an area corresponding to the reflective display area.
From this viewpoint, another liquid crystal display device of the present invention has a liquid crystal layer sandwiched between a pair of substrates, and a transmissive display region for performing transmissive display and a reflective display region for performing reflective display in one dot region. In a liquid crystal display device provided separately, a thickness of the liquid crystal layer between the reflective display area and the transmissive display area is provided between at least one of the pair of substrates and the liquid crystal layer. Is provided at least in the reflective display region, and the thickness of the liquid crystal layer in the central portion of the dot region is set smaller than that in the peripheral portion in the one dot region. I do.
[0016]
According to this configuration, for example, a reflective display area is formed in a rectangular shape at the center of one dot area, a rectangular insulating film is formed therein, and a transmissive display area is formed around the rectangular insulating film. Then, the alignment directions of the liquid crystal molecules are defined in four directions perpendicular to each side of the rectangle with the center of the insulating film in the center of the dot region. As a result, regions having four different orientation directions are formed in one dot region, and an orientation division structure can be realized, so that a wider viewing angle can be achieved.
[0017]
Or, contrary to the above configuration, between at least one of the pair of substrates and the liquid crystal layer, the thickness of the liquid crystal layer of the reflective display region and the transmissive display region, An insulating film that varies depending on its own film thickness may be provided at least in the reflective display region, and the thickness of the liquid crystal layer at the peripheral portion of the dot region in the one dot region may be set smaller than that at the central portion. . More specifically, the reflective display area is provided so as to surround the transmissive display area in one dot, and an insulating film is provided in an area corresponding to the reflective display area around the dot.
[0018]
According to this configuration, for example, a transmissive display area is formed in a rectangular shape in the center of one dot area, a rectangular frame-like insulating film is formed outside the transmissive display area, and a reflective display area is formed around the insulating film. Then, the orientation directions of the liquid crystal molecules are defined in four directions perpendicular to each side of the rectangular frame from the insulating film around the dot region toward the center. As a result, as in the case of the above configuration, regions having four different orientation directions are formed in one dot region, and an orientation division structure can be realized, so that a wider viewing angle can be achieved.
[0019]
Further, it is preferable that the insulating film includes an inclined region having an inclined surface near the boundary between the reflective display region and the transmissive display region so that its film thickness changes continuously.
[0020]
The end of the insulating film near the boundary between the reflective display area and the transmissive display area may have a step-like step. In that case, the above-mentioned step near the boundary between the reflective display area and the transmissive display area As a result, the thickness of the liquid crystal layer changes abruptly, and the alignment of the liquid crystal is disturbed, which may adversely affect the display. In this regard, if an inclined surface is formed in the insulating film so that the film thickness of the insulating film changes continuously, the alignment state of the liquid crystal continuously changes according to the position of the inclined surface of the insulating film. Disorder of the alignment does not occur, and display defects can be avoided. If the insulating film has a rectangular shape as described above, the inclined surfaces also incline in four directions orthogonal to each other, and the presence of the inclined surfaces makes it possible to form the orientation division structure more smoothly.
[0021]
Further, an electrode for driving a liquid crystal layer may be provided on the substrate on which the insulating film is provided, and at least a part of the inclined surface of the insulating film may be provided with an electrode-free region where the electrode does not exist. good.
[0022]
As described above, in the structure of the present invention, the control of the alignment direction can be achieved only by providing the insulating film serving as the protrusion protruding toward the liquid crystal layer, but at least a part of the inclined surface of the insulating film is achieved. When an electrode-free region where no electrode is provided is provided, an electric field (potential line) generated between the electrodes on both substrates is distorted in the vicinity of the electrode-free region, and the action of the distorted electric field causes the orientation direction of the liquid crystal molecules. Can be more easily realized.
[0023]
Suppose that the central portion of one dot is a rectangular reflective display region, the peripheral portion is a transmissive display region, and a rectangular frame-shaped electrode non-formation region is formed in an inclined region of the insulating film corresponding to a boundary between the reflective display region and the transmissive display region. If provided, the electrodes in the reflective display area and the electrodes in the transmissive display area are completely separated, making it difficult to simultaneously apply the same drive voltage to both. Therefore, it is preferable that the electrodes in the reflective display region and the electrodes in the transmissive display region provided on both sides of the electrode non-formation region are electrically connected to each other through a connection portion formed of the same layer as the electrodes. Alternatively, it is preferable that the electrodes in the reflective display region and the electrodes in the transmissive display region are electrically connected to each other through a connection portion formed of a different layer from these electrodes. With this configuration, the same drive voltage can be easily applied simultaneously to the electrodes in the reflective display area and the electrodes in the transmissive display area.
[0024]
Further, when the one substrate is an element substrate having a pixel electrode and a switching element, and the other substrate is a counter substrate having a common electrode and the insulating film, the pixel electrode and the pixel electrode on the one substrate It is desirable to arrange a contact hole for electrically connecting the switching element to a position not overlapping the inclined region in a plane.
[0025]
Since the contact hole for electrically connecting the pixel electrode and the switching element is formed in the upper layer of one of the substrates, the contact electrode portion is usually in a state where the pixel electrode is depressed. Therefore, in the case of the above configuration, the electric field distorted in the vicinity of the electrode non-formation region is further distorted due to the depression of the pixel electrode, and the alignment of the liquid crystal molecules can be more easily controlled.
[0026]
Further, when an electrode for driving a liquid crystal layer and an insulating film are provided over one of a pair of substrates and an electrode for driving a liquid crystal layer is provided over the other substrate, the other substrate It is preferable that the electrode provided has a window outside the inclined region of the insulating film.
[0027]
As described above, in the structure of the present invention, the control of the alignment direction can be achieved only by providing the insulating film serving as a protrusion protruding toward the liquid crystal layer, but the control on the other substrate facing the insulating film can be achieved. If an electrode is provided with a window so as to be located outside the inclined region of the insulating film, after all, there is no electrode in the window, so the electric field generated between the electrodes on both substrates is The oblique electric field makes it possible to more smoothly control the alignment direction of the liquid crystal molecules by the action of the oblique electric field.
[0028]
Further, when the insulating film has an inclined surface, it is preferable that an inclination angle of the inclined surface of the insulating film with respect to the substrate surface is in a range of 5 ° to 50 °. Note that the inclined surface may be flat or curved. The “inclination angle of the inclined surface” here refers to a position where the layer thickness of the inclined region is h / 2, where h is the layer thickness of the flat portion of the insulating film 101, as shown in FIG. The angle θ between the tangent S of the inclined surface 101a and the substrate surface 102 (flat surface).
[0029]
If the inclination angle is less than 5 °, the surface becomes a gentle inclined surface, the size of the inclined region becomes large, and the optical loss increases due to too many portions where the retardation is halfway. On the other hand, if the inclination angle exceeds 50 °, a steeply inclined surface is formed. Therefore, when a non-selection voltage is applied, the liquid crystal molecules are vertically aligned with respect to the inclined surface, so that discrimination with the liquid crystal molecules on the flat surface occurs. Nations occur. As a result, black floating (light leakage) occurs, which causes a decrease in contrast. Therefore, the inclination angle is desirably in the range of 5 ° to 50 °.
[0030]
The contour of the insulating film in one dot region is not particularly limited, but if it is a regular polygon or a circle, the liquid crystal molecules are evenly distributed in each direction in one dot region. The orientation is divided. As a result, the viewing angle at which the contrast is good can be isotropically widened.
Further, by providing circularly polarized light incidence means for causing circularly polarized light to be incident on the one substrate and the other substrate, favorable display can be performed in both reflective display and transmissive display.
[0031]
An electronic apparatus according to the present invention includes the liquid crystal display device according to the present invention. According to this configuration, it is possible to provide an electronic device including a liquid crystal display portion that is bright, has high contrast, and has a wide viewing angle regardless of the use environment.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The liquid crystal display device of this embodiment is an example of an active matrix liquid crystal display device using a thin film transistor (hereinafter, abbreviated as TFT) as a switching element.
[0033]
FIG. 1 is an equivalent circuit diagram of a plurality of dots arranged in a matrix forming an image display area of the liquid crystal display device of the present embodiment, and FIG. 2 is a plan view showing a structure of a plurality of adjacent dots of a TFT array substrate. FIG. 3 and FIG. 3 are cross-sectional views showing the structure of the liquid crystal device, and are cross-sectional views along the line AA ′ in FIG. In the following drawings, the scale of each layer and each member is different in order to make each layer and each member have a size recognizable in the drawings.
[0034]
In the liquid crystal display device of the present embodiment, as shown in FIG. 1, a plurality of dots arranged in a matrix forming an image display area include a pixel electrode 9 and a switching element for controlling the pixel electrode 9. Are formed, and the data line 6a to which an image signal is supplied is electrically connected to the source of the TFT 30. The image signals S1, S2,..., Sn to be written to the data lines 6a are supplied line-sequentially in this order or supplied to a plurality of adjacent data lines 6a for each group. The scanning lines 3a are electrically connected to the gates of the TFTs 30, and the scanning signals G1, G2,..., Gm are applied to the plurality of scanning lines 3a in a pulsed line-sequential manner at a predetermined timing. The pixel electrode 9 is electrically connected to the drain of the TFT 30. When the TFT 30 serving as a switching element is turned on for a predetermined period, the image signals S1, S2,... Write at the timing of
[0035]
The image signals S1, S2,..., Sn of a predetermined level written in the liquid crystal through the pixel electrodes 9 are held for a certain period between the common electrodes described later. The liquid crystal modulates light by changing the orientation and order of the molecular assembly depending on the applied voltage level, thereby enabling gray scale display. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the common electrode. Note that reference numeral 3b is a capacitance line.
[0036]
Next, a planar structure of a TFT array substrate included in the liquid crystal device according to the present embodiment will be described with reference to FIG.
As shown in FIG. 2, a plurality of rectangular pixel electrodes 9 (outlined by dotted lines 9A) are provided in a matrix on the TFT array substrate, and each pixel electrode 9 extends along the vertical and horizontal boundaries of the pixel electrodes 9. A data line 6a, a scanning line 3a, and a capacitance line 3b are provided. In the present embodiment, one dot region is inside a region where each pixel electrode 9 and the data line 6a, the scanning line 3a, the capacitor line 3b, and the like provided so as to surround each pixel electrode 9 are formed. The structure is such that display is possible for each dot region arranged in a matrix.
[0037]
The data line 6a is electrically connected to a source region, which will be described later, of the semiconductor layer 1a constituting the TFT 30, for example, a polysilicon film via the contact hole 5, and the pixel electrode 9 is connected to the semiconductor layer 1a. Among them, it is electrically connected to a drain region described later via a contact hole 8. In addition, the scanning line 3a is arranged to face the channel region (the diagonally shaded region ascending in the figure) of the semiconductor layer 1a, and the scanning line 3a functions as a gate electrode in a portion facing the channel region. .
[0038]
The capacitance line 3b is formed from a main line portion extending substantially linearly along the scanning line 3a (that is, a first region formed along the scanning line 3a when viewed in plan) and a portion intersecting the data line 6a. And a projection (ie, a second region extending along the data line 6a when viewed in a plan view) protruding forward (upward in the figure) along the data line 6a. In FIG. 2, a plurality of first light-shielding films 11a are provided in a region indicated by oblique lines rising to the right.
[0039]
More specifically, the first light-shielding film 11a is provided at a position covering the TFT 30 including the channel region of the semiconductor layer 1a as viewed from the TFT array substrate side, and further, is opposed to the main line of the capacitor line 3b. A main line portion extending linearly along the scanning line 3a, and a protruding portion protruding from a location intersecting the data line 6a toward a subsequent stage (that is, downward in the drawing) adjacent to the data line 6a. The tip of the downward projection in each stage (pixel row) of the first light-shielding film 11a overlaps the tip of the upward projection of the capacitor line 3b in the next stage below the data line 6a. A contact hole 13 for electrically connecting the first light-shielding film 11a and the capacitance line 3b to each other is provided in the overlapping portion. That is, in the present embodiment, the first light-shielding film 11 a is electrically connected to the preceding or subsequent capacitive line 3 b by the contact hole 13.
[0040]
As shown in FIG. 2, a rectangular reflective film 20 is formed at the center of one dot region. The region where the reflective film 20 is formed becomes a reflective display region R, and the reflective film 20 around the reflective display region R. The area where is not formed is the transmissive display area T. Further, a rectangular insulating film 21 is formed so as to include a region where the reflective film 20 is formed when viewed in a plan view.
[0041]
Next, a sectional structure of the liquid crystal display device of the present embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. 2. The present invention is characterized by the configuration of the insulating film at the center of the dot, and the cross-sectional structure of the TFT and other wiring is different from the conventional one. Therefore, illustration and description of TFTs and wiring portions are omitted.
[0042]
As shown in FIG. 3, a liquid crystal layer 50 made of a liquid crystal whose initial alignment state is vertical alignment is sandwiched between the TFT array substrate 10 and an opposing substrate 25 arranged opposite thereto. In the TFT array substrate 10, a reflective film 20 made of a metal film having high reflectivity such as aluminum or silver is formed on the surface of a substrate main body 10A made of a translucent material such as quartz or glass. As described above, the area where the reflective film 20 is formed becomes the reflective display area R, and the area where the reflective film 20 is not formed becomes the transmissive display area T.
[0043]
A dye layer 22R constituting a color filter for reflective display is provided on the reflective film 20 located in the reflective display area R, and a color filter for transmissive display is formed on a substrate located in the transmissive display area T. A coloring dye layer 22T is provided. Generally, in a transflective liquid crystal display device, light is transmitted twice through a color filter in a reflective display, but only once in a transmissive display. There is a problem that is different. Therefore, the present applicant has proposed a technique for changing the color purity of the dye layer of the color filter between the reflective display area and the transmissive display area to improve the balance between the display colors in the reflective display and the transmissive display. Each of the dye layers of the above-mentioned color filter for reflective display and color filter for transmissive display adopts this technology.
[0044]
An insulating film 21 is formed at a position corresponding to the reflective display region R on the dye layers 22R and 22T of the reflective display color filter and the transmissive display color filter. The insulating film 21 is made of, for example, an organic film such as an acrylic resin having a thickness of about 2 to 3 μm, and has an inclined surface near the boundary between the reflective display region R and the transmissive display region T so that its layer thickness changes continuously. It has an inclined region K provided with 21a. Since the thickness of the liquid crystal layer 50 where the insulating film 21 does not exist is about 4 to 6 μm, the thickness of the liquid crystal layer 50 in the reflective display region R is about half the thickness of the liquid crystal layer 50 in the transmissive display region T. That is, the insulating film 21 functions as a liquid crystal layer thickness control layer that varies the layer thickness of the liquid crystal layer 50 between the reflective display region R and the transmissive display region T depending on its thickness. The angle θ between the surfaces of the dye layers 22R and 22T of the color filter and the inclined surface 21a of the insulating film 21 is about 5 ° to 50 °. In the case of the present embodiment, the edge of the flat surface above the insulating film 21 and the edge of the reflective film 20 (reflective display area) substantially match, and the inclined area K is included in the transmissive display area T. .
[0045]
Then, on the surface of the TFT array substrate 10 including the surface of the insulating film 21, the pixel electrode 9 made of a transparent conductive film such as indium tin oxide (hereinafter abbreviated as ITO) and the alignment made of polyimide or the like. A film 23 is formed.
[0046]
On the other hand, on the counter substrate 25 side, a common electrode 31 made of a transparent conductive film such as ITO and an alignment film 33 made of polyimide or the like are formed on a substrate body 25A made of a light-transmitting material such as glass or quartz. Both the alignment films 23 and 33 of the TFT array substrate 10 and the counter substrate 25 are subjected to vertical alignment processing.
[0047]
Although not shown, a circularly polarizing plate is provided on the outer surface side of the TFT array substrate 10, and a circularly polarizing plate is also provided on the outer surface side of the counter substrate 25.
[0048]
According to the liquid crystal display device of the present embodiment, the thickness of the liquid crystal layer 50 in the reflective display region R is reduced to approximately half the thickness of the liquid crystal layer 50 in the transmissive display region T by providing the insulating film 21 in the reflective display region R. Since the size can be reduced, the retardation in the reflective display region R and the retardation in the transmissive display region T can be made substantially equal, thereby improving the contrast. Further, since the insulating film 21 protrudes toward the liquid crystal layer 50 and the insulating film 21 becomes a projection, the liquid crystal molecules 50B are vertically aligned in the initial state as schematically shown in FIG. And a pretilt corresponding to the shape of the projection. By this operation, the orientation direction of the liquid crystal molecules 50B when an electric field is applied can be controlled, so that a display with high contrast can be realized without display defects such as light leakage.
[0049]
That is, according to the configuration of the present embodiment, by providing the transflective liquid crystal display device in the vertical alignment mode with the insulating film 21, it is possible to solve the problem of the decrease in contrast due to the retardation difference in both the reflective and transmissive display modes. At the same time, display defects due to the inability to control the alignment direction of the liquid crystal molecules in the vertical alignment mode can be suppressed. As a result, both the advantage of the vertical alignment mode and the advantage of the transflective type can be utilized, and a liquid crystal display device with excellent display quality can be realized.
[0050]
In the case of the present embodiment, a rectangular reflective display region R is provided at the center of one dot region, and a rectangular insulating film 21 is provided at a position corresponding to the reflective display region R at the center of the dot region. Therefore, the alignment directions of the liquid crystal molecules are defined in four directions perpendicular to each side of the rectangle with the center of the insulating film 21 at the center of the dot. As a result, regions (domains) having four different orientation directions are formed in one dot region, and an orientation division structure can be realized, so that a wider viewing angle can be achieved.
[0051]
Further, the insulating film 21 has an inclined region K near the boundary between the reflective display region R and the transmissive display region T, and the alignment state of the liquid crystal molecules 50B is also continuous according to the position of the inclined surface 21a of the insulating film 21. , The large alignment disturbance does not occur, and display defects can be avoided. In addition, the inclined surfaces 21a of the insulating film 21 are also inclined in four directions orthogonal to each other, and the presence of the inclined surfaces 21a allows the orientation division structure to be formed smoothly.
[0052]
[Second embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as that of the first embodiment, except that a common electrode is provided with a window for controlling alignment. Therefore, in FIGS. 4 and 5, the same components as those in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description will be omitted.
[0053]
In the case of this embodiment, as shown in FIGS. 4 and 5, the configuration on the TFT array substrate 10 side is not different from that of the first embodiment, but the common electrode 31 on the counter substrate 25 has a window. A portion 31M is provided. Two windows 31M are provided for one dot, and are formed in a rectangular shape elongated in a direction along the data line 6a in plan view. The window 31M is formed at a position outside the inclined region K of the insulating film 21.
[0054]
As described in the first embodiment, in the structure of the present invention, the control of the alignment direction can be achieved only by providing the insulating film serving as a protrusion protruding toward the liquid crystal layer. However, when the window 31M is provided on the common electrode 31 on the opposite substrate 25 facing the insulating film 21 so as to be located outside the inclined region K of the insulating film 21 as in the present embodiment, the window 31M Since there is no electrode in the portion, the electric field generated between the electrodes on both substrates is inclined obliquely, and the control of the alignment direction of the liquid crystal molecules 50B can be realized more smoothly by the effect of the oblique electric field. The broken line shown in the liquid crystal layer 50 in FIG. 5 is a potential line, and the liquid crystal molecules 50B are aligned along the potential line, so that the insulating film 21 smoothly aligns without causing disclination.
[0055]
The shape of the window is not limited to that shown in FIG. 4, and may be formed in a rectangular ring shape corresponding to, for example, four-directional domains. However, in this case, since the inside and outside of the window portion need to be electrically connected as one electrode, the inside and outside of the window portion are connected at an arbitrary point instead of a completely continuous rectangular ring. It is desirable.
[0056]
[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as the first and second embodiments, except for the position of the insulating film. Therefore, in FIG. 6, the same components as those in FIGS. 3 and 5 are denoted by the same reference numerals, and detailed description is omitted.
[0057]
In the first and second embodiments, the insulating film 21 is provided at the center of one dot, whereas in the present embodiment, as shown in FIG. The insulating film 21 is disposed on the side. Correspondingly, only one window portion 31M is provided for one dot, and is disposed outside the inclined region K of the insulating film 21.
[0058]
In the present embodiment, since the insulating film 21 is not located at the center of the dot, as in the first and second embodiments, four domains are formed so as to be substantially equally formed in one dot. The alignment of the liquid crystal molecules 50B is not controlled. However, it is possible to eliminate the problem of contrast reduction due to the retardation difference in both the reflection and transmission display modes, and to suppress the display failure due to the inability to control the alignment direction of the liquid crystal molecules in the vertical alignment mode. The same effects as those of the first and second embodiments can be achieved in that they can be realized. In this embodiment, as in the second embodiment, the window 31M is formed. However, the broken line shown in the liquid crystal layer 50 in FIG. 6 is a potential line, and the liquid crystal molecules 50B become potential lines. Since the alignment is performed along, the alignment is smoothly performed without generating disclination due to the insulating film 21.
[0059]
[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS.
FIG. 7 is a plan view showing the structure of a plurality of dots adjacent to each other on the TFT array substrate. FIG. is there.
The basic configuration of the liquid crystal display device of this embodiment is substantially the same as that of the first to third embodiments, except that the positional relationship between the reflective display region R and the transmissive display region T is reversed, The form is different. 7 and 8, the same components as those in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0060]
In the TFT array substrate of the present embodiment, as shown in FIG. 7, a rectangular frame-shaped reflection film 20 is formed around one dot area, and the area where this reflection film 20 is formed is reflected. The display area R becomes the area where the reflective film 20 is not formed becomes the transmissive display area T. That is, in the first to third embodiments, the inside of one dot region is the reflective display region R and the outside is the transmissive display region T, but in the present embodiment, the reverse is the case. Further, a rectangular frame-shaped insulating film 21 is formed so as to include a region where the reflective film 20 is formed when viewed in a plan view.
[0061]
As for the cross-sectional structure, as shown in FIG. 8, a reflective film 20 made of a metal film having a high reflectivity such as aluminum or silver is formed on the TFT array substrate 10. As described above, the area where the reflective film 20 is formed becomes the reflective display area R, and the area where the reflective film 20 is not formed becomes the transmissive display area T. A dye layer 22R constituting a reflective display color filter is provided on the reflective film 20 located in the reflective display region R, and a dye constituting the transmissive display color filter is provided on a substrate located in the transmissive display region T. A layer 22T is provided. An insulating film 21 is formed at a position corresponding to the reflective display region R on each of the dye layers 22R and 22T of the reflective display color filter and the transmissive display color filter. The insulating film 21 has, near the boundary between the reflective display region R and the transmissive display region T, an inclined region K provided with an inclined surface 21a whose layer thickness changes continuously. In the case of the present embodiment, the edge of the flat surface above the insulating film 21 and the edge of the reflective film 20 (reflective display area) substantially match, and the inclined area K is included in the transmissive display area T.
[0062]
The pixel electrode 9 made of a transparent conductive film such as ITO is formed on the surface of the TFT array substrate 10 including the surface of the insulating film 21. However, in the first to third embodiments, the pixel electrode 9 is formed over the entirety of one dot region, whereas in the present embodiment, the pixel electrode 9 is formed on the flat surface of the insulating film 21. However, the pixel electrode 9 is not formed on the inclined surface 21a, and is an electrode non-formed region 9N.
[0063]
FIG. 7 is a plan view of this, and in FIG. 7, the portion where the pixel electrode 9 is present is shown by oblique lines falling to the right. That is, the insulating film 21 has a concave portion having an inverted truncated square pyramid at the center of the dot region, and the pixel electrode 9 is not formed on the inclined surface 21a. Therefore, a substantially rectangular frame-shaped electrode non-forming region 9N is provided. However, if the electrode non-formation area 9N has a rectangular frame shape, the outer (reflective display area R) electrode and the inner (transmissive display area T) electrode are completely separated. Therefore, the pixel electrode 9 in the reflective display region R and the pixel electrode 9 in the transmissive display region T are electrically connected to each other via a connection portion 9C made of ITO in the same layer as the electrodes. With this configuration, the same drive voltage can be simultaneously applied to both the pixel electrodes 9 in the reflective display region R and the transmissive display region T. Note that the connection portion 9C may be formed in a layer different from the pixel electrode 9, and may be connected to the pixel electrode 9 via a contact hole. As shown in FIG. 8, an alignment film 23 made of polyimide or the like is formed on the entire surface of the substrate so as to cover the pixel electrode 9 and the inclined surface 21a of the insulating film 21.
[0064]
On the other hand, on the counter substrate 25 side, a common electrode 31 made of a transparent conductive film such as ITO and an alignment film 33 made of polyimide or the like are formed on a substrate body 25A made of a light-transmitting material such as glass or quartz. Both the alignment films 23 and 33 of the TFT array substrate 10 and the counter substrate 25 are subjected to vertical alignment processing.
[0065]
Also in the present embodiment, the same effects as those of the first to third embodiments can be obtained. That is, as described in the above embodiment, in the structure of the present invention, the control of the alignment direction can be achieved only by providing the insulating film 21 serving as a protrusion protruding toward the liquid crystal layer. However, in the present embodiment, since the pixel electrode 9 does not exist on the inclined surface 21a of the insulating film 21, the electric field generated between the electrodes on both substrates is distorted near the inclined region K, and Control of the alignment direction of the liquid crystal molecules 50B can be more smoothly realized by the distortion. A broken line p shown in the liquid crystal layer 50 of FIG. 8 is a potential line, and the liquid crystal molecules 50B are aligned along the potential line p. Therefore, the insulating film 21 smoothly aligns without causing disclination.
[0066]
[Fifth Embodiment]
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as that of the fourth embodiment, except for the size of the electrode non-forming region. Therefore, in FIGS. 9 and 10, the same reference numerals are given to the same components as those in FIGS. 7 and 8, and the detailed description is omitted.
[0067]
In the fourth embodiment, the entirety of the insulating film 21 on the inclined surface 21a is the electrode non-formation region 9N. In the present embodiment, as shown in FIGS. Only a part of the inclined surface 21a of 21 is a slit-shaped electrode non-forming region 9N. In both the fourth and fifth embodiments, the electrode non-formation region 9N is provided only when the mask pattern is formed in such a shape at the time of patterning the pixel electrode 9, so that the electrode non-formation region 9N is not provided. There is no particular change in the manufacturing process as compared to the one.
[0068]
Also in the present embodiment, since the non-electrode-forming region 9N where the pixel electrode 9 does not exist is provided on the inclined surface 21a of the insulating film 21, the electric field generated between the electrodes on both substrates is distorted in this region. The same effect as in the fourth embodiment, in which the control of the alignment direction of the liquid crystal molecules 50B can be further smoothed by the distortion of the electric field, can be obtained. In addition, the shape, the formation position, and the like of the electrode non-formation region 9N in the fourth and fifth embodiments are not particularly limited to the above example, and can be appropriately changed.
[0069]
[Sixth Embodiment]
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as that of the fourth embodiment, and only defines the inclination angle of the inclined surface of the insulating film. Therefore, in FIG. 11, the same reference numerals are given to the same components as those in FIG. 8, and the detailed description will be omitted.
[0070]
In the case where the area of the transmissive display region T is relatively large in one dot region (for example, the area ratio of the transmissive display region T is 50% or more), as shown in FIG. The film 20 is extended, and the inclined region K of the insulating film 21 is set as a reflective display region R. In the fourth embodiment (FIG. 8), the reflective film 20 is not formed below the inclined region K of the insulating film 21, and the inclined region K of the insulating film 21 is a transmissive display region T. . Further, the inclination angle θ of the inclined surface 21a of the insulating film 21 is defined to be approximately 50 °.
[0071]
In the inclined region K, the retardation has a halfway value in both the transmissive display region T and the reflective display region R, and this region is a factor that degrades the display quality. In this embodiment, since this region is included in the reflective display region R, the display quality of the transmissive display is not deteriorated, although the quality of the reflective display is slightly inferior. Therefore, if anything, it is a configuration suitable for a transflective liquid crystal display device that emphasizes transmissive display.
[0072]
[Seventh Embodiment]
Hereinafter, a seventh embodiment of the present invention will be described with reference to FIG.
FIG. 12 is a cross-sectional view illustrating the configuration of the liquid crystal display device of the present embodiment. 12, the same components as those in the cross-sectional view of the above embodiment such as FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0073]
In the liquid crystal display device of the present embodiment, as shown in FIG. 12, a liquid crystal layer 50 composed of liquid crystal whose initial alignment state is vertical alignment is provided between a TFT array substrate 10 and an opposing substrate 25 disposed opposite thereto. It is pinched. On the counter substrate 25, a dye layer 22R forming a reflective display color filter and a dye layer 22T forming a transmissive display color filter are provided. An insulating film 21 is formed at a position corresponding to the reflective display region R on the dye layers 22R and 22T of the reflective display color filter and the transmissive display color filter. The common electrode 31 is formed on the insulating film 21 and the dye layer 22T of the transmission display color filter. Also in the case of the present embodiment, the insulating film 21 has the inclined surface 21a, but the common electrode 31 is not formed on the inclined surface 21a, and it is an electrode non-formed region 31N.
[0074]
The TFT 110 is formed on the TFT array substrate 10. The TFT 110 includes a semiconductor layer 111 having a source region 111s, a drain region 111d, and a channel region 111c, a gate insulating film 112, and a gate electrode 113. A source line 114 (data line) is connected to the source region 111s, and a drain electrode 115 is connected to the drain region 111d. The pixel electrode 9 is connected to the drain electrode 115 via a contact hole 117 provided in the interlayer insulating film 116. In the present embodiment, the contact hole 117 is connected to the insulating film on the counter substrate 25 side. 21 is disposed at a position below the dye layer 22T (flat surface) of the color filter for transmissive display without overlapping the inclined region K in a plane.
[0075]
In the case of the present embodiment, the orientation of the liquid crystal molecules 50B can be controlled by the shape effect of the insulating film 21 provided on the counter substrate 25 side, and an electrode non-forming region where the common electrode 31 is not provided on the inclined surface 21a of the insulating film 21. By providing 31N, the alignment of the liquid crystal molecules 50B can be further controlled. In addition, the electric field generated in the liquid crystal layer 50 is reduced by the fact that the contact hole 117 is arranged in a region on the TFT array substrate 10 corresponding to a flat surface that does not overlap the inclined region K of the insulating film 21 in a plane. Distortion occurs in the vicinity of the hole 117, and the control of the orientation direction of the liquid crystal molecules 50B can be more smoothly realized by the distortion of the electric field. A broken line p shown in the liquid crystal layer 50 of FIG. 12 is a potential line, and the liquid crystal molecules 50B are aligned along the potential line p, so that the liquid crystal molecules 50B are smoothly aligned without occurrence of disclination.
[0076]
[Electronics]
Next, a specific example of an electronic apparatus including the liquid crystal display device according to the above embodiment of the present invention will be described.
FIG. 14 is a perspective view showing an example of a mobile phone. In FIG. 14, reference numeral 500 denotes a mobile phone main body, and reference numeral 501 denotes a display unit using the liquid crystal display device.
[0077]
FIG. 15 is a perspective view showing an example of a portable information processing device such as a word processor or a personal computer. In FIG. 15, reference numeral 600 denotes an information processing device, reference numeral 601 denotes an input unit such as a keyboard, reference numeral 603 denotes an information processing device main body, and reference numeral 602 denotes a display unit using the liquid crystal display device.
[0078]
FIG. 16 is a perspective view showing an example of a wristwatch-type electronic device. In FIG. 16, reference numeral 700 indicates a watch main body, and reference numeral 701 indicates a display unit using the liquid crystal display device.
[0079]
Since the electronic devices shown in FIGS. 14 to 16 include the display portion using the liquid crystal display device of the above embodiment, the liquid crystal display portion having high brightness, high contrast, and wide viewing angle can be provided regardless of the use environment. It is possible to realize an electronic device provided with the electronic device.
[0080]
The technical scope of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, an example in which the present invention is applied to an active matrix type liquid crystal display device using a TFT as a switching element has been described. However, an active matrix type liquid crystal display device using a thin film diode (TFD) switching element has been described. The present invention can also be applied to a passive matrix type liquid crystal display device or the like. In addition, specific descriptions regarding materials, dimensions, shapes, and the like of various components can be appropriately changed.
[0081]
【The invention's effect】
As described above in detail, according to the present invention, in the transflective liquid crystal display device, it is possible to eliminate the problem of contrast reduction due to a retardation difference in both the reflective and transmissive display modes, and to reduce the liquid crystal molecules in the vertical alignment mode. Display defects due to the inability to control the orientation direction can be suppressed, and as a result, a liquid crystal display device with excellent display quality can be realized. Further, depending on the arrangement of the insulating film, an orientation division structure can be realized, and a wide viewing angle can be achieved.
[Brief description of the drawings]
FIG. 1 is an equivalent circuit diagram of a plurality of dots arranged in a matrix forming an image display area of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a plan view showing a structure of a plurality of dots adjacent to each other on a TFT array substrate constituting the liquid crystal display device.
FIG. 3 is a cross-sectional view showing the structure of the liquid crystal display device, which is a cross-sectional view taken along line AA ′ of FIG. 2;
FIG. 4 is a plan view showing a structure of a plurality of dots adjacent to each other on a TFT array substrate constituting a liquid crystal display device according to a second embodiment of the present invention.
5 is a cross-sectional view showing the structure of the liquid crystal display device, which is a cross-sectional view taken along line AA ′ of FIG. 4;
FIG. 6 is a sectional view illustrating a structure of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 7 is a plan view illustrating a structure of a plurality of dots adjacent to each other on a TFT array substrate constituting a liquid crystal display device according to a fourth embodiment of the present invention.
8 is a cross-sectional view showing the structure of the liquid crystal display device, which is a cross-sectional view taken along the line AA ′ of FIG. 7;
FIG. 9 is a plan view showing a structure of a plurality of dots adjacent to each other on a TFT array substrate constituting a liquid crystal display device according to a fifth embodiment of the present invention.
FIG. 10 is a cross-sectional view showing the structure of the liquid crystal display device, which is a cross-sectional view taken along line AA ′ of FIG. 9;
FIG. 11 is a sectional view illustrating a structure of a liquid crystal display device according to a sixth embodiment of the present invention.
FIG. 12 is a sectional view illustrating a structure of a liquid crystal display device according to a seventh embodiment of the present invention.
FIG. 13 is a view for explaining an inclination angle of an insulating film in the present invention.
FIG. 14 is a perspective view illustrating an example of an electronic apparatus of the invention.
FIG. 15 is a perspective view illustrating another example of the electronic apparatus of the invention.
FIG. 16 is a perspective view showing still another example of the electronic apparatus of the present invention.
[Explanation of symbols]
9 Pixel electrode
10 TFT array substrate
20 Reflective film
21 Insulating film
21a Inclined surface
25 Counter substrate
31 Common electrode
31M window
50 liquid crystal layer
R reflective display area
T Transparent display area

Claims (15)

A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are individually provided in one dot region,
The liquid crystal layer is a liquid crystal layer in which the initial alignment state exhibits vertical alignment, and between the liquid crystal layer and at least one of the pair of substrates, the reflection display region and the transmission display region A liquid crystal display device, wherein an insulating film for varying the thickness of the liquid crystal layer according to its own film thickness is provided at least in the reflective display region. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are individually provided in one dot region,
Between at least one of the pair of substrates and the liquid crystal layer, an insulating film that varies the thickness of the liquid crystal layer between the reflective display region and the transmissive display region according to its own film thickness is provided. A liquid crystal display device provided at least in the reflective display area, wherein the thickness of the liquid crystal layer in the central part of the one dot area is set smaller than that in the peripheral part. The transmission display area is provided so as to surround the reflection display area in the one dot, and the insulating film is provided in an area corresponding to the reflection display area at the center of the dot. 3. The liquid crystal display device according to 1 or 2. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are individually provided in one dot region,
Between at least one of the pair of substrates and the liquid crystal layer, an insulating film that varies the thickness of the liquid crystal layer between the reflective display region and the transmissive display region according to its own film thickness is provided. A liquid crystal display device provided at least in the reflective display area, wherein a thickness of the liquid crystal layer at a peripheral portion of the one dot region is set smaller than that at a central portion. The reflective display area is provided so as to surround the transmissive display area in the one dot, and the insulating film is provided in a peripheral area of the dot corresponding to the reflective display area. 5. The liquid crystal display device according to 1 or 4. 6. The insulating film according to claim 1, wherein the insulating film includes an inclined region having an inclined surface near its boundary between the reflective display region and the transmissive display region so that its film thickness changes continuously. The liquid crystal display device according to claim 1. An electrode for driving the liquid crystal layer is provided on the substrate on the side where the insulating film is provided, and at least a part of the inclined surface of the insulating film is provided with an electrode-free region where the electrode does not exist. The liquid crystal display device according to claim 6, wherein: The electrode in the reflective display area and the electrode in the transmissive display area provided on both sides of the electrode non-formation area are electrically connected to each other through a connection portion formed of the same layer as the electrodes. The liquid crystal display device according to claim 7. An electrode in the reflective display area and an electrode in the transmissive display area provided on both sides of the electrode non-formation area are electrically connected to each other through a connection portion made of a layer different from these electrodes. The liquid crystal display device according to claim 7. The one substrate is an element substrate including a pixel electrode and a switching element, and the other substrate is a counter substrate including a common electrode and the insulating film, and the pixel electrode and the pixel electrode on the one substrate. The liquid crystal display device according to any one of claims 7 to 9, wherein a contact hole for electrically connecting the switching element is arranged at a position not overlapping the inclined region in a plan view. An electrode for driving the liquid crystal layer and the insulating film are provided on one of the pair of substrates, and an electrode for driving the liquid crystal layer is provided on the other substrate, and the other is provided. The liquid crystal display device according to any one of claims 7 to 9, wherein the electrode provided on the substrate side has a window outside the inclined region of the insulating film. The liquid crystal display device according to claim 6, wherein an inclination angle of the inclined surface of the insulating film with respect to a substrate surface is in a range of 5 ° to 50 °. The liquid crystal display device according to claim 2, wherein an outline of the insulating film in the one dot region is a regular polygon or a circle. The liquid crystal display device according to claim 1, further comprising a circularly polarized light incident unit that causes the circularly polarized light to be incident on the one substrate and the other substrate. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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