KR100623984B1 - Liquid crystal displays having wide viewing angle and panels for the same - Google Patents

Abstract

Liquid crystal display for securing a wide viewing angle. A plurality of pixel electrodes are formed on the first substrate, and a common electrode having a recessed pattern formed to be located at a portion corresponding to the pixel electrode is formed on the second substrate facing the first substrate. At this time, the side wall of the recessed pattern forms an angle between 30 ° and 120 ° with the first substrate. At this time, the depression pattern is formed by the depression formed in the color filter. In this way, the viewing angle of the liquid crystal display device can be widened by a simple process, and a liquid crystal display device of excellent image quality can be obtained.

LCD, Wide Viewing Angle, Color Filter, Opening, Recessed Pattern, Vertical Orientation

Description

Wide viewing angle liquid crystal display device and substrate used therefor {LIQUID CRYSTAL DISPLAYS HAVING WIDE VIEWING ANGLE AND PANELS FOR THE SAME}

1 is a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention;

2A and 2B are cross-sectional views of a liquid crystal display according to a first exemplary embodiment of the present invention, in which the sidewalls of the recessed pattern formed in the color filter are 90 ° to the substrate and 45 ° to the substrate, respectively. A diagram showing a transmittance curve,

3 is a plan view of a liquid crystal display according to a second exemplary embodiment of the present invention;

4 is a cross-sectional view taken along line IV-IV 'of FIG. 3,

5 is a cross-sectional view for explaining the effect of the present invention and contrasted with FIG.

6 is a plan view of a liquid crystal display according to a third exemplary embodiment of the present invention;

7 is a plan view of a liquid crystal display according to a fourth exemplary embodiment of the present invention.

The present invention relates to a wide viewing angle liquid crystal display device.

In general, a liquid crystal display device has a structure in which a liquid crystal is injected between two substrates, and the amount of light transmitted is controlled by adjusting the intensity of the electric field applied thereto.

A vertically aligned twisted nematic (VATN) type liquid crystal display includes a pair of transparent substrates having transparent electrodes formed on an inner surface thereof, a liquid crystal material between two transparent substrates, and an outer surface of each transparent substrate. It consists of two polarizers attached to and polarizing light. In the state in which the electric field is not applied, the liquid crystal molecules are vertically oriented with respect to the two substrates, and when the electric field is applied, the liquid crystal molecules filled between the two substrates are parallel to the substrate and twisted in a spiral with a constant pitch.

In the case of the VATN liquid crystal display, the liquid crystal molecules are vertically aligned with respect to the substrate in the state in which no electric field is applied, and thus, when a polarizing plate is used, the light may be completely blocked in the state in which the electric field is not applied. That is, since the luminance of the off state is very low in the normally black mode, a high contrast ratio may be obtained as compared with a conventional twisted nematic liquid crystal display. However, in a state where an electric field is applied, particularly in a state where a gradation voltage is applied, as in the normal twisted nematic mode, there is a problem in that the viewing angle is narrow due to a large difference in retardation of light depending on the viewing direction of the liquid crystal display. .

In order to solve this problem, various methods of patterning electrodes and forming a plurality of regions using fringe fields have been proposed. In US Pat. No. 5,309,264, Lien proposed a method of forming an X-shaped opening in a common electrode, and Histake et al. Proposed a method of alternately forming openings in an electrode formed in an upper and lower substrate in US Pat. No. 5,434,690. .

However, when forming the split alignment using the above method, a separate mask is required to pattern the common electrode, and in a structure without a protective film on the color filter, since the pigment of the color filter affects the liquid crystal material, There is a problem in that a protective film must be formed and the foreground is severely generated at the edge of the patterned electrode.

An object of the present invention is to provide a wide viewing angle liquid crystal display device without the above problems.

Another object of the present invention is to improve the image quality of a wide viewing angle liquid crystal display.

In order to solve this problem, the common electrode is formed to have a recessed pattern.

Specifically, a plurality of pixel electrodes are formed on the first substrate, and a common electrode having a recessed pattern formed to be located at a portion corresponding to the pixel electrode is formed on the second substrate facing the first substrate. At this time, the side wall of the recessed pattern forms an angle between 30 ° and 120 ° with the first substrate.

In addition, a storage capacitor electrode and a plurality of pixel electrodes are formed on the first substrate. A common electrode having a recessed pattern located at a portion corresponding to the pixel electrode is formed on the second substrate facing the first substrate. At this time, when the first substrate is viewed from above, the pixel electrode completely covers the storage capacitor electrode at least at a constant portion.

Next, a structure of a thin film transistor substrate for a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the drawings.

1 is a cross-sectional view of a liquid crystal display according to a first exemplary embodiment of the present invention.

The liquid crystal display device includes a liquid crystal material which is injected between the lower substrate 10 and the upper substrate 60 facing the lower substrate 10 and the lower substrate 10 and the upper substrate 60 and is oriented perpendicular to the substrates 10 and 60. 90).

On the lower substrate 10 made of a transparent insulating material such as glass, a pixel electrode 50 made of a transparent conductive material such as indium tin oxide (ITO) or indium tin oxide (IZO) and having an opening pattern 51 is formed. Each pixel electrode 50 is connected to the switching element 11 to receive an image signal voltage. In this case, a thin film transistor is generally used as the switching element 11, and the thin film transistor is connected to a gate line (not shown) for transmitting a scan signal and a data line (not shown) for transmitting an image signal, respectively. The pixel electrode 50 is turned on in off according to the scan signal. The lower polarizer 14 is attached to the lower surface of the lower substrate 10. In this case, the pixel electrode 50 may not be made of a transparent material in the case of a reflective liquid crystal display, and in this case, the lower polarizer 14 may also be unnecessary.

It is also made of a black matrix 70 to prevent light leakage on the lower surface of the upper substrate 60 made of a transparent insulating material such as glass, a color filter 61 of red, green, and blue and a transparent conductive material such as ITO or IZO. The common electrode 80 is formed.

At this time, a depression is formed in the color filter 61. Therefore, the common electrode 80 formed on the color filter 61 has a depression pattern 81 along the depression of the color filter 61.

The black matrix 70 is formed not only on the periphery of the pixel region but also on the recessed pattern 81 and the upper portion of the common electrode 80. This is to prevent light leakage caused by the recessed pattern 81 as will be described later.

On the other hand, the recessed pattern 81 portion of the common electrode 80 is in contact with the black matrix 70. Although the black matrix 70 may be formed of an organic material, it is generally formed of a conductive material such as chromium. When the black matrix 70 is formed of a conductive material, the black matrix 70 may also serve as a conductive path for transmitting the common electrode 80 signal to reduce the common electrode resistance.

The reason why a wide viewing angle can be obtained through such a structure will be described.

In the state in which no electric field is applied to the liquid crystal display, the liquid crystal molecules 90 remain vertically aligned with the two substrates 10 and 60, and thus exhibit the same black state as when there is no recession pattern in the common electrode.

When an electric field is applied, as shown in FIG. 1, the electric field perpendicular to the substrates 10 and 60 is formed in most places, but the common electrode 80 is the color filter near the depression formed by the color filter 61 being removed. It is formed in a curved shape along the pattern of Therefore, the equipotential surfaces between the two substrates are not formed in parallel with the two substrates 10 and 60 and are bent in accordance with the shape of the common electrode 80. As a result, the electric field is also not formed perpendicular to the substrates 10 and 60 but is formed in a slightly inclined direction.

Since the liquid crystal has negative dielectric anisotropy, the alignment direction of the liquid crystal molecules is to be perpendicular to the direction of the electric field. Accordingly, the long axis of the liquid crystal molecules near the recessed pattern 81 is twisted while being inclined with respect to the surfaces of the two substrates 10 and 60. In this case, two regions in which the inclination directions of the liquid crystal molecules are opposite to each other based on the center line of the recessed pattern 81 are formed, and optical properties of the two regions are compensated for each other, thereby widening the viewing angle.

As shown in FIG. 1, when the recessed pattern 81 is formed on the common electrode 80 by removing a part of the color filter 61, the split alignment may be formed in a simpler process as compared to the rubbing method. The advantage is that the arrangement of molecules can be very fine-tuned to different regions or made into many different shapes.

Meanwhile, only a part of the thickness of the color filter 61 may be removed and a part thereof may be formed in a remaining state.

Now, a method of manufacturing a color filter substrate for a liquid crystal display according to an embodiment of the present invention will be described.

First, a black matrix is formed by forming and patterning a layer of metal or black resist such as chromium on a substrate.

Next, a color filter having a groove is formed by applying and patterning a resist of one of red, green, and blue, and sequentially applying and patterning the remaining two resists to form a three color filter. Complete

Alternatively, red, green, and blue resists may be sequentially applied and patterned to form a color filter, and then grooves may be formed in three color filters at a time.

Finally, a transparent conductive material such as ITO is deposited on the black matrix and the color filter to form a common electrode. When the common electrode is formed, the common electrode may be cut off due to a step near the groove formed in the color filter.

The relationship between the shape of the recessed pattern and the image quality of the liquid crystal display will now be described.

2A and 2B are cross-sectional views of a liquid crystal display according to a first exemplary embodiment of the present invention, in which the sidewalls of the recessed pattern formed in the color filter are respectively 90 ° with respect to the substrate and 45 ° with respect to the substrate, respectively. It is a figure which shows a transmittance curve.

In the case of FIG. 2A, the equipotential surface is severely curved only under the recessed pattern of the common electrode 80 and above the opening of the pixel electrode 50. Therefore, the light transmittance also changes drastically only at the part with the recessed pattern and the opening. Therefore, if only the portion where the recessed pattern is formed, the texture does not appear. However, in FIG. 2B, the equipotential surface is severely curved not only below the recessed pattern of the common electrode 80 and above the opening of the pixel electrode 50 but also around the recessed pattern. The transmittance of light also changes rapidly in the recessed pattern and the portion having the opening, as well as the periphery of the recessed pattern. Therefore, the texture appears around the recessed pattern.

As can be deduced above, the smaller the angle between the sidewall of the recessed pattern and the substrate is, the more the texture spreads around the recessed pattern. Therefore, the larger the angle formed by the sidewall of the recessed pattern with the substrate, the better. The angle formed between the side wall of the recessed pattern and the substrate is an angle measured from the side where the color filter 61 is filled. This angle may exceed 90 °. However, when the angle is 120 ° or more, the common electrode formed of a material such as indium tin oxide (ITO) is likely to be cut at the recessed pattern portion.

In FIG. 2B, the texture appears around the recessed pattern even when the angle between the sidewall of the recessed pattern and the substrate is 45 °, but the display quality is not significantly reduced. In addition, it is possible to adjust to some extent by changing the width of the recessed pattern, the width of the opening of the pixel electrode, and the like. Therefore, the lower limit of the angle between the side wall and the substrate is about 30 degrees.

A liquid crystal display according to a second embodiment of the present invention will be described.

3 is a plan view of a liquid crystal display according to a second exemplary embodiment of the present invention, FIG. 4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3, and FIG. 5 is a cross-sectional view illustrating the effect of the present invention. This is in contrast to the drawing.

The gate line 20 is formed in the horizontal direction on the lower insulating substrate 10. The gate electrode 21 is formed in the gate line 20 in the form of a protrusion. Two common electrode lines 21 and 22 are formed on the insulating substrate 10 in parallel with the gate line 20. The two common electrode lines 21 and 22 are connected to each other by two storage capacitor electrodes 23 and 24 formed in the longitudinal direction. At this time, the number of the common electrode lines 21 and 22 may be three or more, or may form in a single line. The gate line 20, the gate electrode 21, the common electrode lines 21 and 22, and the storage capacitor electrodes 23 and 24 are made of metal such as aluminum or chromium. At this time, they may be formed by a single layer, or may be formed by a double layer formed by successively laminating a chromium layer and an aluminum layer. In addition, a variety of metals may be used to form the gate wiring and the common wiring.

A gate insulating film 31 made of silicon nitride (SiNx) or the like is formed on the gate line 20, the common electrode lines 21 and 22, and the storage capacitor electrodes 23 and 24.

The data line 40 is formed in the vertical direction on the gate insulating film 31. A source electrode 41 is formed in the data line 40 as a branch, and a drain electrode 42 is formed adjacent to the source electrode 41. The data line 40, the source electrode 41, and the drain electrode 42 are also made of a material such as chromium and aluminum, similarly to the gate wiring. It can also be formed in a single layer or multiple layers.

The lower portion of the source electrode 41 and the drain electrode 42 is a contact for reducing a contact resistance between the semiconductor layer (not shown) used as the channel portion of the thin film transistor and the source and drain electrodes 41 and 42 and the semiconductor layer. Layers (not shown) are formed but not shown. The semiconductor layer is usually formed using amorphous silicon, and the contact layer is formed using amorphous silicon heavily doped with n-type impurities.

On the data line 40 or the like, a protective film 32 made of an inorganic insulator such as silicon nitride or an organic insulator such as resin is formed. The protective film 32 is provided with a contact hole (not shown) for exposing the drain electrode 42.

The pixel electrode 50 having the opening pattern 51 is formed on the passivation film 32. The pixel electrode 50 is formed using a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO) or an opaque conductor having excellent light reflection characteristics such as aluminum (Al). The opening pattern 51 formed in the pixel electrode 50 has a horizontal opening formed in a horizontal direction at a position that half-divides the pixel electrode 50 and a diagonal direction in the upper and lower portions of the pixel electrode 50 divided in half. It includes the diagonal opening formed in the. At this time, the upper and lower diagonal openings are perpendicular to each other. This is to evenly distribute the direction of the fringe field in four directions.

At this time, the storage capacitor electrodes 23 and 24 are formed so as to be completely covered by the pixel electrode 50 in the A, B, C, and D portions when the liquid crystal display device is viewed from above.

A black matrix 70 is formed on the upper insulating substrate 60 to prevent light leakage. On the black matrix 70, red, green, and blue color filters 61 having depressions are formed. The common electrode 80 having the recessed pattern 81 of the color filter 61 is formed on the color filter 61. At this time, the depression pattern 81 is formed due to the depression of the color filter 61. The common electrode 80 is formed of a transparent conductor such as ITO or indium zinc oxide (IZO).

The recessed pattern 81 of the common electrode 80 includes an oblique opening portion of the pixel electrode 50 in the center, and includes an oblique portion parallel to the side and a refraction portion overlapping the sides of the pixel electrode 50. At this time, the refraction portion is classified into a longitudinal refraction portion and a horizontal refraction portion. Among the portions A, B, C, and D of the pixel electrode 50 overlapping with the vertical refraction portion, the pixel electrode 50 completely covers the storage capacitor electrodes 23 and 24 thereunder. This will prevent the texture lines from appearing.

4 and 5, the reason why the texture is prevented in the liquid crystal display according to the present invention will be described.

First, referring to FIG. 5, the cause of the texture occurring in the liquid crystal display will be described.

FIG. 5 illustrates the shape of electric field lines and liquid crystal molecules arranged thereby when an electric field is applied between the common electrode 800 and the pixel electrode 500. As shown in FIG. 5, a strong electric field is formed between the storage capacitor electrodes 230 and 240 and the edges of the pixel electrode. This electric field affects the electric field around the pixel region. This effect is particularly large at portions A, B, C, and D in which the recessed pattern 81 of the common electrode 800 is formed. As a result, a fringe field inclined in a direction opposite to the center portion of the pixel region is formed around the pixel region. Therefore, the arrangement direction of the liquid crystal molecules is reversed in the portion T between the peripheral portion and the central portion of the pixel region. This part (T) appears as a texture on the screen.

Next, the reason why the texture is prevented in the liquid crystal display according to the present invention will be described with reference to FIG. 4.

In FIG. 4, the pixel electrode 50 completely covers the storage capacitor electrodes 23 and 24. Therefore, the electric field lines formed between the pixel electrode 50 and the storage capacitor electrodes 23 and 24 are mostly connected to the lower surface of the pixel electrode 50. As a result, the electric field formed between the storage capacitor electrodes 23 and 24 does not affect the liquid crystal molecules. The fringe field unaffected by the storage capacitor electrodes 23 and 24 maintains a constant orientation in the pixel region and changes its inclined direction only when it reaches a point outside the pixel region (the part covered by the black matrix). As a result, a portion T in which the arrangement direction of the liquid crystal molecules is reversed also appears in a portion outside the pixel region. This part is covered by the black matrix so no texture appears on the screen.

A liquid crystal display according to a third embodiment of the present invention will be described.

6 is a plan view of a liquid crystal display according to a third exemplary embodiment of the present invention.

In the liquid crystal display device according to the third embodiment, the basic structure such as wiring and thin film transistor is the same as that of the second embodiment. However, the shape of the opening pattern 51 of the pixel electrode 50 and the recessed pattern 81 of the common electrode is different from the planar shape of the storage capacitor electrode 24 and the common electrode line 21.

The opening 51 includes a horizontal opening formed in the horizontal direction and a vertical opening formed in the vertical direction. The recessed pattern 81 may include a circumferential portion formed to overlap the edge of the pixel electrode 50 and a horizontal portion formed between two horizontal openings.

The opening 51 and the recessed pattern 81 overlap each other to divide the pixel electrode 50 into a plurality of small regions. Each small region forms a polygon in which the two longest sides are parallel to each other. This is for shortening the response time of the liquid crystal molecules. That is, the direction in which the liquid crystal molecules are arranged by the fringe field formed by the opening 51 and the recessed pattern 81 may be in parallel with each other. This shortens the response time because the operation of the liquid crystal molecules is completed by only one step operation.

Also in the liquid crystal display according to the second exemplary embodiment, the small region divided by the opening 51 and the recessed pattern forms a polygon in which the two longest sides are parallel to each other.

The common electrode line 21 is formed as a single line extending in the horizontal direction but may be formed in plural. In the common electrode line 21 line, the recessed pattern 81 overlaps with a horizontal part. The storage capacitor electrode 24 is formed parallel to the left and right sides of the pixel electrode 50 and is covered by the pixel electrode 50. This is to prevent the generation of the texture as in the second embodiment.

A liquid crystal display according to a fourth embodiment of the present invention will be described.

In the liquid crystal display according to the fourth embodiment, only the shape of the opening 51 of the pixel electrode 50 and the recessed pattern 81 of the common electrode and the planar shape of the storage capacitor electrode 24 and the common electrode line 21 are second. And the third embodiment.

The openings 51 in the fourth embodiment are formed of several X-shapes. The recessed pattern 81 includes a circumferential portion and a horizontal portion and is formed in a form to isolate each of the X-shaped openings 51.

The common electrode line 21 is formed as a single line extending in the horizontal direction but may be formed in plural. In the common electrode line 21 line, the recessed pattern 81 overlaps with one of the horizontal parts. The storage capacitor electrode 24 is formed parallel to the left and right sides of the pixel electrode 50 and is covered by the pixel electrode 50.

As in the embodiment of the present invention, when the grooves are formed in the color filter to form the divided-aligned liquid crystal display device, the viewing angle of the liquid crystal display device can be widened in a simple process, and the response speed is high and the liquid crystal display device having excellent image quality can be obtained. Can be.

Claims (35)

Board, A color filter formed on the substrate and having a recessed pattern; It includes a common electrode formed on the color filter, And a sidewall of the recessed pattern formed in the color filter forms an angle between 30 ° and 120 ° with respect to the substrate surface. In claim 1, Further comprising a black matrix formed on the substrate, A portion of the black matrix is formed so as to overlap the recessed pattern. First substrate, A plurality of pixel electrodes formed on the first substrate, A second substrate facing the first substrate, The common electrode formed on the second substrate and having a recessed pattern positioned in a portion corresponding to the pixel electrode. Including; The sidewalls of the recessed pattern may form an angle between 30 ° and 120 ° with the first substrate. In claim 3, A color filter formed between the second substrate and the common electrode and having a recessed pattern; The depression pattern of the common electrode is formed by the depression pattern of the color filter. In claim 3, And a black matrix formed on the second substrate and partially overlapping the recessed pattern of the common electrode. In claim 5, The recessed pattern portion of the common electrode is in contact with the black matrix. In claim 3, And a storage capacitor electrode formed on the first substrate. The pixel electrode completely covers the storage capacitor electrode at least at a constant portion when the first substrate is viewed from above. In claim 7, And a predetermined portion where the pixel electrode completely covers the storage capacitor electrode is a portion where the recessed pattern formed on the common electrode and the side of the pixel electrode overlap each other. In claim 7, And one storage capacitor electrode each positioned on the left and right sides of the pixel electrode. In claim 7, The storage capacitor electrode is a branch-shaped electrode extending from the common electrode line and is electrically connected to the common electrode line. In claim 10, The common electrode line overlaps the recessed pattern. In claim 7, The pixel electrode has an opening pattern. In claim 12, The opening pattern of the pixel electrode may include a horizontal opening formed in a horizontal direction at a position that divides the pixel electrode up and down, and a diagonal opening formed in a diagonal direction in the upper and lower portions of the pixel electrode divided in half. The diagonal openings are perpendicular to each other, The recessed pattern of the common electrode includes an oblique portion parallel to the side of the pixel electrode with an oblique portion parallel to the diagonal opening of the opening pattern. In claim 13, And a predetermined portion of the pixel electrode completely covering the branch electrode extending from the common electrode is a portion in which the refraction portion of the recess pattern overlaps the vertical side of the pixel electrode. In claim 1, And the aperture pattern of the pixel electrode and the recessed pattern of the common electrode are divided to divide the pixel electrode into a plurality of small regions, and the small region is a polygon in which two longest sides are parallel to each other. The method of claim 15, The small region is classified into a first small region having a longest two sides in a first direction and a second small region in a second direction, wherein the first direction and the second direction form an angle between 85 ° and 95 °. Display device. The method of claim 16, And the first direction is a diagonal direction with respect to the side of the pixel electrode. The method of claim 16, And the first direction is parallel to one of the top, bottom, left, and right sides of the pixel electrode. First substrate, A storage capacitor electrode formed on the first substrate, A plurality of pixel electrodes formed on the first substrate, A second substrate facing the first substrate, The common electrode formed on the second substrate and having a recessed pattern positioned in a portion corresponding to the pixel electrode. Including; The pixel electrode completely covers the storage capacitor electrode at least at a constant portion when the first substrate is viewed from above. The method of claim 19, And a predetermined portion where the pixel electrode completely covers the storage capacitor electrode is a portion where the recessed pattern formed on the common electrode and the side of the pixel electrode overlap each other. First substrate, A pixel electrode formed on the first substrate, A sustain electrode formed on the first substrate, A second substrate facing the first substrate, A common electrode formed on the second substrate and having a recessed pattern And the pixel electrode completely covering the sustain electrode in a predetermined region. The method of claim 21, The depression portion overlaps with a predetermined region of the edge of the pixel electrode. First substrate, A color filter formed on the first substrate and having depressions; A common electrode formed on the color filter, A second substrate facing the first substrate, A pixel electrode formed on the second substrate and having a cutout, A pixel region formed between the pixel electrode and the common electrode Wherein the depression is formed in the pixel region. The method of claim 23, The depth of the depression is less than the thickness of the color filter liquid crystal display device. The method of claim 24, And a black matrix formed on the first substrate. The method of claim 25, A portion of the black matrix overlaps the depression. The method of claim 23, When the liquid crystal display is viewed from the front, the depression and the cutout form a closed curved surface. The method of claim 26, When the liquid crystal display is viewed from the front, the depression and the cutout form a closed curved surface. The method of claim 28, And the recess and the cutout are symmetrically arranged to each other. The method of claim 29, A liquid crystal layer interposed between the first substrate and the second substrate and including a liquid crystal having negative dielectric anisotropy, First and second alignment layers formed on the common electrode and the pixel electrode, respectively, and align the major axis of the liquid crystal to be perpendicular to the first and second substrates; and First and second polarizing plates attached to the outside of the first substrate and the second substrate, respectively. Liquid crystal display further comprising. From paragraph 30 And a polarization axis of the first polarizing plate and the second polarizing plate perpendicular to each other. The method of claim 31, The closed curved surface defined by the depression and the cutout is divided into four types according to the average long axis direction of the liquid crystal located therein. 33. The method of claim 32, The long axis directions of the liquid crystal form 40 to 50 ° with respect to the polarization axis of the polarizer. Board, A black matrix formed on the substrate and surrounding a pixel area and having a portion located in the pixel area, A color filter formed on the substrate and having a depression overlapping a portion of the black matrix, A common electrode formed on the color filter and having a depression formed by the depression of the color filter; Liquid crystal display comprising a. The method of claim 34, And a depth of the depression of the color filter is shallower than a thickness of the color filter.

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