KR102166050B1 - Blacklight Unit and Liquid Crystal Display Device having the same - Google Patents

Abstract

The present invention discloses a backlight unit and a liquid crystal display device having the same. A liquid crystal display device of the disclosed invention includes a liquid crystal display panel; And a light source for supplying a surface light source to the liquid crystal display panel, a light guide plate for converting light incident from the light source into a surface light source, an optical sheet disposed on the light guide plate, the light guide plate, optical sheet, and light sources. It includes a backlight unit including a reflector, and is bent from the side surfaces along the four sides of the reflective plate in parallel with the lower surface of the reflector, the first and the first and the second surrounding the light source, the light guide plate and the optical sheet. Includes 2 supports.
The backlight unit of the present invention and a liquid crystal display having the same are effective in implementing a flexible element and a narrow bezel area by removing the support main and the lower cover used in the liquid crystal display.

Description

Backlight unit and liquid crystal display device having the same {Blacklight Unit and Liquid Crystal Display Device having the same}

The present invention relates to a liquid crystal display, and more particularly, a backlight unit capable of implementing a narrow bezel area and a flexible device by removing a support main and a lower cover used in the liquid crystal display device, and It relates to a liquid crystal display device.

Recently, a liquid crystal display device has been in the spotlight as a next-generation high-tech display device with low power consumption, good portability, and high added value.

Among these liquid crystal displays, the active matrix liquid crystal display equipped with a thin film transistor, which is a switching element that can control the voltage on and off for each pixel, is the most noticeable due to its excellent resolution and video realization ability. Receiving.

In general, a liquid crystal display device forms an array substrate and a color filter substrate, respectively, through an array substrate manufacturing process for forming a thin film transistor and a pixel electrode, and a color filter substrate manufacturing process for forming a color filter and a common electrode, and between the two substrates. It is completed through the cell process through the liquid crystal.

However, since the liquid crystal display does not have its own light-emitting element, a separate light source is required to display the difference in transmittance as an image. To this end, a backlight unit with a built-in light source is arranged on the back of the liquid crystal display panel. do.

Such a backlight unit is divided into a direct type and an edge type according to the location of the light source, and the direct type backlight unit places the light source under the liquid crystal display panel to direct light emitted from the light source. The light guide plate is disposed under the LCD panel, and the light source is disposed on at least one side of the light guide plate, so that the light guide is emitted from the light source using refraction and reflection from the light guide plate. It is a method of indirectly supplying light to the LCD panel.

Here, as the light source of the backlight unit, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) has been widely used. According to the trend of lightweighting, light emitting diodes (LEDs), which have advantages in power consumption, weight, and brightness, are replacing fluorescent lamps.

In general, in a liquid crystal display device, a backlight unit including a light source, a light guide plate, optical sheets, and a reflecting plate is accommodated inside a lower cover, and a liquid crystal display panel is fixed to the support main above the backlight unit, and then the upper cover is provided with the support. It is assembled in the form of a single liquid crystal display module while being fastened with the main and lower covers.

The support main is formed in the shape of a square frame made of a plastic material, and the lower cover is formed of a metal suspension (SUS) or an aluminum (Al) mold.

In the liquid crystal display as described above, since the support main and the lower cover are formed of a hard material, it is difficult to implement a flexible backlight unit or a flexible display device.

In addition, since the support main serves to support the liquid crystal display panel, a certain thickness and width are required, and there is a limit in reducing the bezel area.

In addition, since the support main and the lower cover are used to assemble the liquid crystal display panel and the backlight unit, it is difficult to reduce the thickness of the liquid crystal display device.

In addition, since the support main and the lower cover are manufactured by injection or mold using a plastic material and metal, the manufacturing cost is high, and the assembly process is complicated.

An object of the present invention is to provide a backlight unit capable of implementing a flexible element and a narrow bezel area by removing a support main and a lower cover used in a liquid crystal display device, and a liquid crystal display device having the same.

In addition, another object of the present invention is to provide a backlight unit in which a reflective plate used in a liquid crystal display device is used as a backlight unit housing and a liquid crystal display panel fixing means to reduce lightness, thinness and manufacturing cost, and a liquid crystal display device having the same. .

The backlight unit of the present invention for solving the problems of the prior art as described above includes a light source, includes a light guide plate for converting light incident from the light source into a surface light source, and includes an optical sheet disposed on the light guide plate And a reflector in which the light guide plate, the optical sheet, and the light source are accommodated, and side surfaces disposed along the four sides of the reflective plate, and are bent parallel to the lower surface of the reflective plate from the side surfaces, and the light source, the light guide plate, and the optical By including the first and second support portions surrounding the sheet, the support main and the lower cover used in the liquid crystal display are removed, thereby implementing a flexible element and a narrow bezel area.

In addition, the liquid crystal display device of the present invention includes a liquid crystal display panel, a light source for supplying a surface light source to the liquid crystal display panel, a light guide plate for converting light incident from the light source into a surface light source, and on the light guide plate And a backlight unit including an optical sheet disposed, and a reflecting plate in which the light guide plate, the optical sheet, and light sources are accommodated, and side surfaces disposed along four sides of the reflecting plate, and parallel to the lower surface of the reflecting plate from the side surfaces. By including the first and second support portions that are bent to surround the light source, the light guide plate, and the optical sheet, the support main and the lower cover used in the liquid crystal display are removed, thereby implementing a flexible element and a narrow bezel area. It works.

The backlight unit and the liquid crystal display having the same of the present invention have an effect of implementing a flexible element and a narrow bezel area by removing a support main and a lower cover used in the liquid crystal display.

In addition, the backlight unit of the present invention and a liquid crystal display device having the same use a reflector used in the liquid crystal display device as a means for accommodating the backlight unit and fixing the liquid crystal display panel, thereby reducing lightness and thickness and reducing manufacturing cost.

1 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.
2A and 2B are cross-sectional views taken along lines I-I' and II-II' of FIG. 1.
3 is a diagram showing the structure of a reflector used in a liquid crystal display device of the present invention.
4A is a view showing a structure of a reflector according to another embodiment of the present invention.
4B is a cross-sectional view taken along line III-III' of FIG. 4A.
5A and 5D are diagrams schematically illustrating a process of assembling the liquid crystal display of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and the present invention is not limited to the illustrated matters. The same reference numerals refer to the same components throughout the specification. In addition, in describing the present invention, when it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

When'include','have','consists of' and the like mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In the case of a description of the positional relationship, for example, if the positional relationship of two parts is described as'upper','upper of','lower of','next to','right' Or, unless'direct' is used, one or more other parts may be located between the two parts.

In the case of a description of a temporal relationship, for example,'after','following','after','before', etc. It may also include cases that are not continuous unless' is used.

First, second, etc. are used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one component from another component. Accordingly, the first component mentioned below may be a second component within the technical idea of the present invention.

Each of the features of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments can be implemented independently of each other or can be implemented together in a related relationship. May be.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the drawings, the size and thickness of the device may be exaggerated for convenience. The same reference numbers throughout the specification denote the same elements.

1 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 2A and 2B are cross-sectional views taken along lines I-I' and II-II' of FIG. 1.

1 to 2B, the liquid crystal display device 100 of the present invention includes a liquid crystal display panel 110, a backlight unit 120, and a top cover 140.

The liquid crystal display panel 110 and the backlight unit 120 are modularized by the top cover 140 and the reflector 150 of the backlight unit 120.

Looking at each of these in more detail, the liquid crystal display panel 110 and the backlight unit 120 are modularized through the top cover 140 and the reflector 150, and the top cover 140 is It has a rectangular frame shape in which the cross section is bent in a “b” shape so as to cover the upper and side edges, and is configured to display an image realized in the liquid crystal display panel 110 by opening the front surface of the top cover 140.

In addition, the liquid crystal display panel 110 and the backlight unit 120 are mounted so that the reflector 150, which is the basis for assembling the entire liquid crystal display device, is a horizontal surface 151 (bottom surface) in close contact with the rear surface of the backlight unit 120 , It consists of a side surface 153 whose edge is vertically bent upward, and first and second support portions 152 and 154 bent inwardly parallel to the horizontal surface 151 from the side surface 153.

The first support portions 152 are opposed to each other from the upper side of the two side surfaces facing each other among the four side surfaces 153 with the horizontal surface 151 therebetween, and the second support portion 154 is the first support portion 152 Are opposed to each other with the horizontal surface 151 therebetween.

That is, the first support part 152 and the second support part 154 are disposed in a direction perpendicular to each other, the liquid crystal display panel 110 is mounted on the first and second support parts 152 and 154, and the reflector The backlight unit 120 is accommodated in the horizontal surface 151 of 150 and inside the first and second support portions 152 and 154.

The top cover 140 may be coupled along the periphery of the reflector 150, and may be referred to as a case top or a top case. The top cover 140 may be formed in a rectangular frame shape, and may be formed in a plastic material or film shape.

However, in some cases, the top cover 140 may be removed.

In addition, the liquid crystal display panel 110 is a part that plays a key role in image display, and includes an array substrate 112 and a color filter substrate 114 bonded to each other with a liquid crystal layer therebetween.

At this time, although not shown in the drawing under the premise of the active matrix method, a plurality of gate lines and data lines cross each other to define a pixel on the inner surface of the array substrate 112, which is usually called a lower substrate or a thin film transistor substrate. A thin film transistor (TFT) is provided at each intersection point, and is connected to a transparent pixel electrode formed in each pixel in a one-to-one correspondence.

In addition, a color filter of red (R), green (G), and blue (B) colors and each of them are covered on the inner surface of the color filter substrate 114 called the upper substrate as an example corresponding to each pixel. A black matrix is provided to cover gate lines, data lines, and thin film transistors. In addition, red (R), green (G), blue (B) color filters and transparent common electrodes covering the black matrix are provided.

However, in the case of an IPS (In-Plane Switching) mode or FFS (Fringe Field Switching) mode liquid crystal display device, a pixel electrode and a common electrode may be disposed in the array substrate 112.

Further, polarizing plates (not shown) that selectively transmit only specific light are attached to the outer surfaces of the array substrate and the color filter substrates 112 and 114, respectively.

The printed circuit board 117 is connected through a connecting member 116 such as a flexible circuit board or a tape carrier package (TCP) along at least one edge of the liquid crystal display panel 110, A hole may be formed in the side surface 153 of the reflective plate 150 or may be properly folded and adhered to the rear surface of the reflecting plate 150 beyond the side surface 153.

In the liquid crystal display panel 110, when the thin film transistor selected for each gate line is turned on by the on/off signal of the gate driving circuit, the signal voltage of the data driving circuit is transmitted to the corresponding pixel electrode through the data line. The arrangement direction of the liquid crystal molecules is changed by the electric field between the pixel electrode and the common electrode, indicating a difference in transmittance.

In addition, the liquid crystal display device according to the present invention is provided with a backlight unit 120 that supplies light from the rear surface of the liquid crystal display panel 110 so that a difference in transmittance is expressed to the outside.

The backlight unit 120 includes an LED assembly 129, a white or silver reflector 150, a light guide plate 123 mounted on the horizontal surface 151 of the reflector 150, and an optical sheet interposed thereon ( 210). The optical sheet 210 may include a quantum dot light conversion sheet.

The LED assembly 129 is located on one side of the light guide plate 123 so as to face the light incident surface of the light guide plate 123, and this LED assembly 129 includes a plurality of LEDs 129a and a plurality of LEDs 129a. It includes a PCB (129b) to be mounted spaced apart.

The LED assembly 129 has a top view type in which light emitted from a plurality of LEDs 129a is perpendicular to the PCB 129b.

At this time, the LED 129a includes a blue LED or red (R), green (G) and blue (B) LEDs that emit blue light having a wavelength of about 430 nm to 450 nm in order to improve luminous efficiency and brightness. I can.

In addition, the LED 129a may be a white (W) LED.

The optical sheet 210 disposed on the light guide plate 123 includes a diffusion sheet, at least one light collecting sheet, a light conversion sheet, and the like, and diffuses or condenses the light passing through the light guide plate 123 to generate the liquid crystal display panel 110. ) To make the surface light source more uniform.

Referring to FIGS. 2A and 2B, a detailed cross-sectional view of an assembly line taken along lines I-I' and II-II' of FIG. 1 is as follows.

The light guide plate 123, the optical sheet 210, and the LED assembly 129 of the backlight unit 120 of the present invention are accommodated inside the reflective plate 150. The side surfaces 153 of the reflector 150 and the first and second support portions 152 and 154 are assembled to surround the light guide plate 123, the optical sheet 210, and the LED assembly 129.

The LED assembly 129 is disposed in the light-incident area of the light guide plate 123, and the first support part 152 of the reflective plate 150 is disposed above the light-incident area of the light guide plate 123 and the LED assembly 129. It is disposed parallel to the upper surface of the light guide plate 123.

In addition, a reflective film 160 is disposed on a lower surface of the first support part 152 corresponding to the light incident part of the light guide plate 123, and the first support part 152 to which the reflective film 160 is attached is a second The upper surface of the light-incident portion of the light guide plate 123 is fixed by the adhesive film T2.

In addition, the liquid crystal display panel 110 is fixed by a first adhesive film T1 on the upper surface of the first support part 152 of the reflective plate 150 corresponding to the light incident part area of the light guide plate 123.

In addition, in the Ⅱ-Ⅱ' area where the LED assembly 129 is not disposed, the light guide plate 123 and the optical sheet 210 are assembled to be wrapped by the side 9153 of the reflector 150 and the second support 154. do. Third and fourth adhesive films T3 and T4 are attached to the lower and upper surfaces of the second support 154 of the reflector 150, respectively.

Therefore, the second support part 154 of the reflective plate 150 is fixed to the optical sheet 210 by a fourth adhesive film T4, and the liquid crystal display panel 110 is attached to the third adhesive film T3. It is fixed to the second support 154 by.

Although illustrated in the drawings, 141 and 142 not described are first and second pads, respectively.

As described above, the backlight unit of the present invention and a liquid crystal display having the same remove the support main and the lower cover used in the conventional liquid crystal display, and change the structure of the reflector to accommodate the backlight unit, thereby implementing a flexible backlight unit. It can have an effect.

In addition, by mounting and fixing the liquid crystal display panel on the support portion of the reflective plate, a narrow bezel area can be implemented, and a flexible liquid crystal display can be implemented.

In addition, in the present invention, by removing the support main and the lower cover used in the conventional liquid crystal display device, there is an effect of reducing the light and thinness of the liquid crystal display device and reducing the manufacturing cost.

3 is a view showing a structure of a reflector used in a liquid crystal display device of the present invention, FIG. 4A is a view showing the structure of a reflector according to another embodiment of the present invention, and FIG. 4B is a III- It is a cross-sectional view taken along line Ⅲ'.

3 to 4B, the reflective plate 150 of the present invention includes a horizontal surface 151 (lower surface) on which components of a backlight unit are stacked, and a side surface 153 that is vertically bent along four sides of the horizontal surface 151. ), and first and second support portions 152 and 154 that are bent in a horizontal direction with the horizontal plane 151 at each of the side surfaces 153.

In the embodiment of the reflector 150 of FIG. 3, when the first and second support portions 152 and 154 are folded in parallel with the horizontal surface 151 of the reflector 150, respectively, the four corner regions of the reflector 150 The height and the height of the first and second support portions 152 and 154 are different.

In this way, when a step is generated between the four corner regions of the reflector 150 and the first and second support portions 152 and 154, the liquid crystal display panel is formed of the first and second support portions 152 and 154. There is a problem that is not supported in all areas.

In the present invention, in order to solve this problem, an edge region of the second support 154 having a larger width X of the first support 152 is removed. Accordingly, even if the first and second support portions 152 and 154 of the reflector 150 are folded parallel to the horizontal plane 151, the height of the periphery of the reflector 150 is maintained at the same height.

In addition, although the edges of the second support part 154 are removed in FIG. 3, the edge regions of both sides of the first support part 152 are removed by the width X of the second support part 154, so that the reflector 150 The first and second support portions 152 and 154 may not overlap each other in the four corner regions of

Therefore, when the thickness D1 of the first support part 152 of the reflector 150 and the thickness D2 of the second support part 154 are equal to each other, the first and The second support portions 152 and 154 form the same plane at the same height.

In this way, if the height of the area around the edge of the reflective plate 150 is the same, the liquid crystal display panel can be brought into contact with all areas of the first and second support portions 152 and 154 and can be supported. There is an effect of assembling the LCD panel to a uniform height.

4A and 4B, the reflector 250 according to another embodiment of the present invention is vertically bent along the horizontal plane 251 (lower surface) on which components of the backlight unit are stacked, and four sides of the horizontal plane 251 And first and second support portions 252 and 254 that are bent in a horizontal direction with the horizontal surface 251 at each of the side surfaces 253 that are formed and the side surfaces 253.

The side portions 252a of the first support portion 252 and the side portions 254a of the second support portion 254 overlap each other in the four corner regions of the reflective plate 250.

Accordingly, the thickness D3 of the side portion 252a of the first support part 252 and the thickness D3 of the side portion 254a of the second support part 254 so as not to cause a step difference in the four corner regions of the reflector 250 ) Were the same as each other.

However, the thickness D4 of the first and second support portions 252 and 254 disposed in regions other than the four corners of the reflector 250 (regions excluding the side portions) is a side portion of the first support portion 252. The height of the first and second support portions 252 and 254 around the edge of the reflective plate 250 was made equal to twice the thickness D3.

As shown in the drawing, the first and second support portions 252 and 254 of the reflector 250 are bent in a direction parallel to the horizontal plane 251, and the first and second support portions 252 and 254 of the reflector 250 The side portions 252a and 254a of the first and second support portions 252 and 253 overlap each other, but the top surface around the edge of the reflector 250 maintains the same height.

Accordingly, the liquid crystal display panel of the present invention has an effect that the entire area of the liquid crystal display panel can be fixedly disposed at the same height by contacting the first and second support portions 252 and 254 of the reflector 250.

5A and 5D are diagrams schematically illustrating a process of assembling the liquid crystal display of the present invention.

In FIGS. 5A to 5D, a description is mainly given of assembling the light guide plate and the optical sheet by the second support part 154 of the reflector 150 in FIGS. 1 and 3, but as shown in FIG. 2, the LED assembly is arranged. The light guide plate incident part area and the other side of the light guide plate are assembled in the same manner.

5A to 5D, a second support 154 is extended from the side 153 of the reflector 150 of the present invention, and the lower and upper surfaces of the second support 154 have third and Fourth adhesive films T3 and T4 are attached.

As shown in FIG. 5B, when the light guide plate 123 and the optical sheet 210 are stacked on the lower surface (horizontal surface) of the reflecting plate 150, the second support part 154 of the reflecting plate 150 is the reflecting plate 150 It is bent horizontally with the lower surface of the. In this case, the second support part 154 is fixed to the optical sheet 210 by a fourth adhesive film T4 attached to the lower surface of the second support part 154.

Then, as shown in FIG. 5D, the liquid crystal display panel 110 is mounted on the second support part 154 of the reflector 150, and the liquid crystal display panel 110 is the second support part 154. The liquid crystal display panel 110 is fixed by the third adhesive film T3 attached to the upper surface.

In addition, although not shown in the drawing, as shown in FIG. 3, the first and second support portions 152 and 154 formed on the reflecting plate 150 are bent parallel to the lower surface 151 of the reflecting plate 150. , The heights of the upper surfaces of the first and second support portions 152 and 154 disposed around the edge of the reflector 150 are the same.

Accordingly, the liquid crystal display panel 110 mounted on the reflective plate 150 may be fixed on the reflective plate 150 at the same height.

As described above, the backlight unit of the present invention and a liquid crystal display having the same have an effect of implementing a flexible device and a narrow bezel area by removing the support main and the lower cover used in the liquid crystal display.

In addition, by using the reflector used in the liquid crystal display device of the present invention as a means for accommodating a backlight unit and fixing a liquid crystal display panel, there is an effect of reducing lightness and thickness and reducing manufacturing cost.

100: liquid crystal display device 110: liquid crystal display panel
112: first substrate 114: second substrate
117: printed circuit board 120: backlight unit
210: optical sheet 123: light guide plate
150: reflector 153: side
152: first support 154: second support

Claims (11)

Light source;
A light guide plate for converting light incident from the light source into a surface light source;
An optical sheet disposed on the light guide plate; And
The light guide plate, the optical sheet, and a reflective plate in which light sources are accommodated,
The reflecting plate includes four side surfaces disposed along the four sides of the reflecting plate, and two first support portions bent parallel to the lower surface of the reflecting plate from the side surfaces to surround at least some of the light source, the light guide plate, and the optical sheet And two second supports,
In the region of the light incident part of the light guide plate in which the light source is disposed on one side, a first support part surrounds the light source and the light guide plate, is attached to the upper surface of the light guide plate, and is spaced apart from the optical sheet,
In another area of the light guide plate in which the light source is not disposed, a second support unit surrounds the light guide plate and the optical sheet and is attached to an upper surface of the optical sheet.
The backlight unit of claim 1, wherein a reflective film is further disposed between a lower surface of the first support part attached to an upper surface of the light guide plate and an upper surface of the light guide plate in the light incident part area of the light guide plate.
The backlight unit as claimed in claim 1, wherein a portion of both side edges of one of the first and second support portions is removed in the four corner regions of the reflector.
delete The method of claim 1, wherein the first and second support portions overlap each other in four corner regions of the reflector, and do not overlap with the thickness of the first and second support portions in a region where the first and second support portions overlap. The backlight unit, characterized in that the thickness in the region is different.
Liquid crystal display panel; And
A light source for supplying a surface light source to the liquid crystal display panel, a light guide plate for converting light incident from the light source into a surface light source, an optical sheet disposed on the light guide plate, and a reflector in which the light guide plate, optical sheet, and light sources are accommodated Including a backlight unit comprising a,
The reflecting plate includes four side surfaces disposed along the four sides of the reflecting plate, and two first support portions bent parallel to the lower surface of the reflecting plate from the side surfaces to surround at least a portion of the light source, the light guide plate, and the optical sheet. And two second supports,
In the region of the light incident part of the light guide plate in which the light source is disposed on one side, a first support part surrounds the light source and the light guide plate, is attached to the upper surface of the light guide plate, and is spaced apart from the optical sheet,
In another area of the light guide plate in which the light source is not disposed, a second support part surrounds the light guide plate and the optical sheet and is attached to an upper surface of the optical sheet.
The method of claim 6, wherein the liquid crystal display panel is fixed on the first support parts and the second support parts,
It is fixed by a first adhesive film on the upper surface of the first support part attached to the upper surface of the light guide plate in the light incident part region of the light guide plate,
It is fixed by a second adhesive film to the upper surface of the second support part attached to the upper surface of the light guide plate in another area of the light guide plate,
The liquid crystal display device, characterized in that the thickness of the first adhesive film is thicker than that of the second adhesive film.
The liquid crystal display device according to claim 6, wherein a reflective film is further disposed between a lower surface of the first support part attached to an upper surface of the light guide plate and an upper surface of the light guide plate in the light incident part area of the light guide plate.
The liquid crystal display device of claim 6, wherein a portion of the edge of either side of one of the first and second support portions is removed in the four corner regions of the reflector.
The liquid crystal display device of claim 6, further comprising a printed circuit board connected to the liquid crystal display panel via a connection member and disposed on a side surface of the reflecting plate adjacent to the light source.
The method of claim 6, wherein the first and second support portions overlap each other in the four corner regions of the reflector, and do not overlap with the thickness of the first and second support portions in the region where the first and second support portions overlap. The liquid crystal display device, characterized in that the thickness in the region is different.

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