KR20040103038A - Liquid crystal display apparatus - Google Patents

Abstract

PURPOSE: An LCD(Liquid Crystal Display) is provided to realize high brightness, to reduce its thickness, to remove a bright-line and a waterfall phenomenon and to reduce the manufacturing cost. CONSTITUTION: A liquid crystal panel(10) displays an image. A PCB(Printed Circuit Board)(40) drives the liquid crystal panel. A backlight assembly(20) comprises the first and second light guide panels(21,22) having a separation interval by a separation member(25) interposed between the panels and illumination members(23,24) for illuminating a light toward the respective light guide panels. The PCB is connected to a TFT(Thin Film Transistor) substrate of the liquid crystal panel through an FPC(Flexible Printed Circuit)(50). The FPC is curved at a corner portion of the backlight assembly, so that the PCB connected to an end of the FPC is arranged to a circumference of the backlight assembly.

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAY APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. More particularly, the thickness of the liquid crystal display device can be reduced while the high brightness can be achieved, and the bright lines and the water fall on the liquid crystal display panel can be removed, and the manufacturing cost can be reduced. It relates to a liquid crystal display device.

A liquid crystal display device applies a voltage to a specific molecular array of a liquid crystal to convert it into another molecular array, and visually changes the optical properties such as birefringence, photoreactivity, dichroism, and light scattering characteristics of the liquid crystal cell that emit light by the molecular array. It is a display device using the modulation of the light by the liquid crystal cell by converting to.

Since the liquid crystal display device is a light-receiving display device that displays an image by controlling the amount of light coming from the outside, a separate light source for illuminating the liquid crystal display panel, that is, a backlight assembly, is required. Here, the liquid crystal display is divided into an edge method and a direct method according to the structure of the backlight assembly.

First, the backlight assembly of the edge-type liquid crystal display device is disposed on the side of the light guide plate for guiding the light, and the light uniformity is good, the durability is long, and it is advantageous for the thinning of the liquid crystal display device. In the case of increasing the size, the luminance is relatively lower than that of the direct type liquid crystal display device, and is mainly applied to a relatively small liquid crystal display device such as a monitor of a laptop computer and a desktop computer.

On the other hand, the direct type backlight assembly is mainly used in a liquid crystal display device having a large screen requiring high luminance because the light utilization efficiency is higher than that of the edge method.

Hereinafter, a conventional direct liquid crystal display device will be described in detail. In addition, unless otherwise indicated, the direction in which the reflecting plate is located is called rear and the direction in which the liquid crystal display panel is located is promised to be front.

As shown in FIG. 1, the conventional direct liquid crystal display device 100 is provided at the rear of the liquid crystal display panel 110 and the liquid crystal display panel 110 on which an image is displayed. A backlight assembly 120 for supplying light, a printed circuit board 140 (PCB) for transmitting an image signal to the liquid crystal display panel 110, and a front edge of the liquid crystal display panel 110 are blocked. It includes a front chassis 160.

The liquid crystal display panel 110 is positioned between a first substrate 114 having a switching element such as a thin film transistor (TFT), a pixel electrode, and the like, and a first substrate 112 and both substrates 112 and 114. Liquid crystals not shown. Here, the image signal applied from the printed circuit board 40 is applied to the thin film transistor of the first substrate 114 via a drive IC (not shown), whereby the liquid crystal receives the signal electrically from the backlight assembly 120. The image is displayed by light.

The backlight assembly 120 is provided at a predetermined distance from the lamp 121 for emitting light, the reflecting plate 122 positioned behind the lamp 121, and the reflecting plate 122 above the lamp 121. The optical sheet layer 123 in which the diffuser plate 123a, the prism sheet 123b, and the like are stacked, and the support frame 124 for receiving the reflecting plate 122 and the optical sheet layer 123 are accommodated.

The reflecting plate 122 is disposed behind the optical sheet layer 123 at a predetermined distance from the optical sheet layer 123, and a plurality of lamps 121 are disposed at predetermined intervals on the front surface of the reflecting plate 122. . The reflective plate 122 reflects the light toward the optical sheet layer 123 toward the rear of the light emitted from the lamp 121 to minimize the loss of light from the lamp 121.

The support frame 124 has a receiving space formed between the front frame 126 and the front frame 126 to be coupled to the rear of the front frame 126 to block the front edge of the optical sheet layer 123 The rear frame 125 accommodates and supports the optical sheet layer 123 and the reflecting plate 122.

Meanwhile, the liquid crystal display panel 110 is disposed in front of the support frame 124 to contact and support the rear edge surface of the liquid crystal display panel 110. An inverter (not shown) for converting a DC current supplied from the outside into an AC current and supplying the lamp 121 to the rear surface of the reflecting plate 122 is disposed.

The printed circuit board 140 is connected to the first substrate 114 of the liquid crystal display panel 110 through the flexible printed circuit (FPC) 150, and the flexible circuit board 150 is connected to the first substrate (FPC). The printed circuit board 140 is bent from the corner of the support frame 124 to the rear end of the rear frame 125.

However, the conventional direct liquid crystal display device 100 has the following disadvantages.

First, as shown in FIG. 2, in the conventional direct liquid crystal display device 100, the immediately front region (the “a” region of FIG. 2) of the lamp 121 is the lamp 121 and the lamp 121. There is a problem in that bright lines are generated in the area of the liquid crystal display panel 110 which is brighter than the front area ("b" area of FIG. 2) in the space between the two spaces.

Second, in order to prevent the bright lines caused by the luminance deviation between the lamps 121 as described above, the distance Q between the lamps 121 and the optical sheet layer 123 should be increased, which is a value of the liquid crystal display 100. You will fall in love with thinning. In addition, when the distance P between the lamps 121 is reduced, the generation of bright lines on the liquid crystal display panel 110 may be reduced. However, this may increase manufacturing costs and increase power consumption.

Third, in the conventional direct type liquid crystal display device 100, since the lamp 121 directly emits light behind the liquid crystal display panel 110 and the optical sheet layer 123, it is generated in the lamp 121. The heat deteriorates the liquid crystal display panel 110 and the optical sheet layer 123, which causes a decrease in luminance due to heat. FIG. 3 illustrates a change in luminance over time during driving of the liquid crystal display device 100 in the conventional direct type liquid crystal display device 100.

Fourth, the inverter for driving the lamp 121 is located close to the back of the reflecting plate 122, that is, the rear of the lamp 121, so that the driving frequency of the lamp 121 and the driving frequency of the inverter are mutually There is a problem in that horizontal noise occurs on the liquid crystal display panel 110 due to interference. In order to solve such a problem, the ITO sheet 123c is installed in front of the diffusion plate 123a, and the ITO sheet 123c has a low light transmittance and thus becomes a factor that hinders the luminance of the liquid crystal display 100. In addition, the manufacturing cost is high and the labor cost increases, which increases the manufacturing cost of the liquid crystal display device 100.

Fifth, in the direct type liquid crystal display device 100, when any one of the plurality of lamps 121 need to be replaced due to a failure or the like, the front chassis 160 and the entire support frame 124 must be opened. There is this.

Accordingly, it is an object of the present invention to provide a liquid crystal display device which can reduce the thickness while realizing high brightness.

In addition, another object of the present invention is to provide a liquid crystal display device capable of eliminating black and white noise (Waterfall) on the liquid crystal display panel and reduce the manufacturing cost.

1 is a schematic cross-sectional view of a conventional liquid crystal display device,

2 is a view showing the distribution of light of the conventional backlight assembly.

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

4 is a schematic cross-sectional view of a liquid crystal display according to a second embodiment of the present invention;

5 to 8 illustrate an assembly step of a backlight assembly according to a second embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

1,1 ', 1 ": liquid crystal display 10: liquid crystal display panel

12: first substrate 14: second substrate

20: backlight assembly 21: first light guide plate

22: second light guide plate 21a, 22b: light diffusion unit

23, 24: lighting unit 23a, 24a: lamp

23b, 24b: lamp reflector 25: separation part

25a: stopper 26: reflector

27: auxiliary reflector 28: support frame

29: front frame 30: rear frame

31 optical sheet layer 31a diffuser plate

31b: prism sheet 40: printed circuit board

50: flexible circuit board 60: front chassis

The above object, according to the present invention,

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail, and the same reference numerals are used for the same components even if the embodiments are different, the description thereof will be omitted.

In the liquid crystal display device 1 according to the first embodiment of the present invention, as shown in FIG. 4, a liquid crystal display panel 10 on which an image is displayed and a rear side of the liquid crystal display panel 10 are provided. The backlight assembly 20 for supplying light to the 10, the printed circuit board 40 (PCB) for applying an image signal to the liquid crystal display panel 10, and the liquid crystal display panel 10 And a front chassis 60 blocking the front soft surface.

The liquid crystal display panel 10 is formed between a first substrate 12 having a switching element such as a thin film transistor (TFT), a pixel electrode, and the like, and a second substrate 14 and both substrates 12 and 14. Liquid crystals not shown. The image signal applied from the printed circuit board 40 is applied to the thin film transistor of 12 via a drive IC (not shown), whereby the liquid crystal receives the signal electrically and receives the image by the light from the backlight assembly 20. Display.

The backlight assembly 20 includes a first light guide plate 21 and a second light guide plate 22 disposed at a rear side of the liquid crystal display panel 10 at a distance from each other, and at least around the edges of the light guide plates 21 and 22. The first lighting unit 23 and the second lighting unit 24 are disposed in one region to illuminate the light guide plates 21 and 22.

A spacer 25 is interposed between the first LGP 21 and the second LGP 22 so that the first LGP 21 and the second LGP 22 have a spaced interval in parallel with each other. Each of the lighting units 23 and 24 is enclosed and supported by the support frame 28 to the outside in the plate direction of each of the light guide plates 30 and 40. Here, the separation unit 25 isolates the first lighting unit 23 and the second lighting unit 24 from each other, thereby eliminating electrical interference between the two lighting units 23 and 24. In addition, the interior of the support frame 28, 10 is divided into a front and rear receiving space by the spacer 25. In the embodiment of the present invention, the spacer 25 and the support frame 28 are integrally formed.

The rear side of the first light guide plate 21 is supported by the spacer 25 so as to be accommodated in the front receiving space of the support frame 28. In addition, the front of the second light guide plate 22 is supported by the spacer 25 so as to be accommodated in the rear receiving space of the support frame 28. That is, the first LGP 21 and the second LGP 22 are disposed to have a predetermined distance from each other by the spacer 25, and are accommodated in the front and rear accommodating spaces of the support frame 28, respectively.

The light diffusion part 21a is provided on the rear side plate surface of the first light guide plate 21. The light diffusing portion 21a diffuses the light from the second light guide plate 22 and the first lighting unit 23 toward the liquid crystal display panel 10, thereby allowing the light diffusion unit 21a to emit light from the second light guide plate 22 and the first lighting unit 23. Light is distributed evenly over the entire area of the liquid crystal display panel 10 to improve the brightness of the liquid crystal display device 1. Here, the light diffusing portion 21a may be provided by forming the rear side plate surface of the first light guide plate 21 in a concave-convex pattern shape, and printing the light diffusion ink on the rear side plate surface of the first light guide plate 21, or Of course, a material capable of scattering light may be mixed into the first light guide plate 21 to provide a light output function.

In addition, the light diffusing portion 22a may be provided on the front side plate surface of the second light guide plate 22. The light diffusing portion 22a provided in the second light guide plate 22 is preferably formed of the same material and shape as the light diffusing portion 21a on the side of the first light guide plate 21.

The first lighting unit 23 and the second lighting unit 24 are respectively installed between the periphery of the edge of the first light guide plate 21 and the second light guide plate 22 and the inner wall surfaces of the front and rear receiving spaces of the support frame 28. The first light guide plate 21 and the second light guide plate 22 emit light.

The first lighting unit 23 and the second lighting unit 24 are lamps 23a and 24a which are light sources that emit light, and light is emitted from each of the lamps 23a and 24a by the first light guide plate 21 and the second light guide plate 22. Lamp reflecting plates 23b and 24b for reflecting light emitted toward the outside of the plate direction in the first light guide plate 21 and the second light guide plate 22. By the configuration of the first lighting unit 23 and the second lighting unit 24, it is possible to minimize the loss of light emitted in the opposite direction of the first light guide plate 21 and the second light guide plate 22. In addition, since the lamps 23a and 24a are provided around the edges of the first and second light guide plates 21 and 22, the distance between the lamps 23a and 24a and the inverter (not shown) installed behind the backlight assembly 20 is relatively large. As a result, horizontal noise generated on the liquid crystal display panel 10 due to mutual interference may be eliminated.

The reflecting plate 26 is provided behind the second light guide plate 22. As the reflecting plate 26, one having a specular reflection function such as silver fusion film or white film can be used. As a result, by reflecting the light transmitted through the rear side plate surface of the second light guide plate 22 and entering it into the second light guide plate 22, it is possible to minimize the loss of light emitted from the lamp 24a of the second lighting unit 24. It becomes possible.

Here, the rear frame 30 is provided at the rear of the reflector plate 26 to shield the rear of the rear receiving space of the support frame 28 in combination with the support frame 28. Here, the back frame 30 is provided with a screw through hole 30a, and the support frame 28 is provided with a screw fastening portion 28a at a position corresponding to the screw through hole 30a. By passing the screw 90 is fastened to the screw fastening portion 28a, the back frame 30 is coupled to the support frame 28. In the embodiment of the present invention, the back frame 30 is described as being coupled to the support frame 28 by a screw 90, but can be coupled by a variety of coupling methods, such as hook bonding or adhesive.

The printed circuit board 40 is connected to the TFT substrate of the liquid crystal display panel 10 through a flexible printed circuit (FPC) 50, and the flexible circuit board 50 is connected to the backlight assembly 20 from the TFT substrate. The printed circuit board 40 is bent at a corner of the edge and connected to an end thereof, and is disposed around one edge of the backlight assembly 20.

Meanwhile, an optical sheet layer 31 may be provided on the front surface of the first light guide plate 21 to improve the quality of the liquid crystal display panel 10. The optical sheet layer 31 includes a diffusion plate 31a for directing light incident from the first light guide plate 21 toward the front direction of the liquid crystal display panel 10 and a prism for improving the luminance of the liquid crystal display device 1. It is preferable to include the sheet 31b.

Since the diffusion plate 31a has a small amount of light incident from the first light guide plate 21 in the front direction and an angle with respect to the normal direction, the light in the normal direction is changed to the front direction by refraction and thus the liquid crystal The front luminance of the display device 1 is improved.

The prism sheet 31b is provided stacked in front of the diffusion plate 31a. Since the light emitted from the diffuser plate 31a has a large viewing angle as the diffused light, the prism sheet 31b narrows the viewing angle of the light emitted from the diffuser plate 31a to improve the front luminance of the liquid crystal display device 1. And reduce power consumption.

The front edge of the first light guide plate 21 and the front edge of the optical sheet layer 31 are blocked by the front frame 29. 3 illustrates that the front frame 29 is provided to surround the outer wall forming the front receiving space of the support frame 28, but the first light guide plate 21, the light guide sheet layer 80, and the support frame 28 are provided. Of course it can be provided so that only the front of the contact. Here, the front frame 29 is coupled to the support frame 28 by various types of coupling structures such as screws, hooks and adhesive members to shield the front. In addition, a support jaw 29a may be provided on the front surface of the front frame 29 to support the liquid crystal display panel 10.

5 is a cross-sectional view of the liquid crystal display device 1 according to the second embodiment of the present invention. As shown in the drawing, the liquid crystal display device 1 ′ according to the second embodiment of the present invention includes the spacer 25 and the second light guide plate between the spacer 25 and the rear side surface of the first light guide plate 21. And an auxiliary reflecting plate 27 interposed between the front side plate surface of the front side 22 and between the front side plate surface of the first light guide plate 21 and the rear surface of the front frame 29. As a result, the light incident from the lamps 23a and 24a to the first light guide plate 21 and the second light guide plate 22 at a predetermined angle is applied to the inside of the first light guide plate 21 and the second light guide plate 22. By reflecting, the loss of light is reduced.

Here, it is preferable that the stopper 25a for preventing the auxiliary reflecting plate 27 from moving inward in the plate surface direction is provided in the spaced portion 25 ′ provided with the auxiliary reflecting plate 27. In addition, it is preferable to provide a stopper 25a that prevents the auxiliary reflecting plate 27 interposed between the first light guide plate 21 and the rear end region of the front frame 29 from moving.

With the above configuration, the assembling process of the liquid crystal display devices 1 and 1 'according to the present invention will be described as an example of the assembling process of the liquid crystal display device 1' according to the second embodiment of the present invention.

First, the support frame 28 is provided on a predetermined work surface such that the rear receiving space of the support frame 28 provided integrally with the spacer 25 faces upward. Then, the second light guide plate 22 is seated on the separation part 25 ′ to place the second light guide plate 22 in the rear receiving space of the support frame 28, and then the reflector plate 26 is disposed on the second light guide plate 22. )

When the above operation is completed, the rear receiving space of the support frame 28 is shielded by the rear frame 30 while the second light guide plate 22 and the reflecting plate 26 are accommodated in the rear receiving space of the supporting frame 28. do. Here, the rear frame 30 may be coupled to the support frame 28 by a screw 90 as described above.

When the fastening of the rear frame 30 is completed, the support frame 28 is turned over so that the front receiving space is turned upward. Then, the first light guide plate 21 is seated on the spaced portion 25 ′ of the support frame 28 to arrange the first light guide plate 21 in the front receiving space of the support frame 28, and then the optical sheet layer ( 31) is mounted on the upper portion of the first light guide plate 21. Next, the front frame 29 is brought into close contact with the edges of the first light guide plate 21 and the optical sheet layer 31 to be seated on the top of the optical sheet layer 31.

When the installation of the front frame 29 is completed, the backlight assembly 20 is inserted by inserting the lighting units 23 and 24 into the space between the support frame 28 and the edge regions of the first and second light guide plates 21 and 22, respectively. ) Assembly is completed. Here, each of the lighting units 23 and 24 is slidably inserted between the support frame 28 and the first and second light guide plates 21 and 22. As described above, each of the lighting units 23 and 24 is slidably inserted between the first and second light guide plates 21 and 22 of the support frame 28 so that the lighting units 23 and 24 may be installed so that the backlight assembly may be replaced when the lamps 23a and 24a are replaced. 20) It can be replaced without disassembling the whole.

On the other hand, the auxiliary reflector 27 is before and after the step of inserting the respective lighting unit (23, 24), the first and second light guide plate (21, 22) and the support frame 28 in the same manner as the insertion method of the lighting unit (23, 24). Can be inserted in between. In addition, of course, the first and second LGPs 21 and 22 may be installed by being seated on the spaced portion 25 ′ of the support frame 28.

After the manufacturing of the backlight assembly 20 is completed by the above process, the liquid crystal display panel 10 is inserted into the support jaw 29a of the front frame 29 and disposed in front of the backlight assembly 20. The front edge of the liquid crystal display panel 10 is blocked by the front chassis 60 to assemble the liquid crystal display device 1 ′.

In the above-described embodiments, two light guide plates 21 and 22 are installed in the liquid crystal display device 1 and 1 ′ according to the present invention, but three or more light guide plates having a predetermined distance from each other may be installed. Of course.

In addition, although the first and second lighting units 23 and 24 according to the present invention are provided in the peripheral area around both edges of the first and second light guide plates 21 and 22, respectively, they are provided only on one side and the rear side of each light guide plate. Of course, the plate surface can be provided to be inclined.

Although light diffusing portions 21a and 22a are provided on the surfaces of the light guide plates 30 and 40 facing each other, as shown in FIG. 6, the second light guide plate 22 'is provided with an optical diffuser portion 22a'. Of course, can be provided on the back.

In the above-described embodiment, although the liquid crystal display device 1 according to the present invention includes the optical sheet layer 31, the first and second light guide plates 21 and 22 and the light guide plates 21 and 22 are used. When the quality of luminance and the like is improved by the light diffusion units 21a and 22a provided, at least one of the optical sheet layers 31 may not be used.

By the above configuration, the effect of the liquid crystal display device 1 according to the present invention is compared with the conventional direct liquid crystal display device 1 and described in detail as follows.

First, the liquid crystal display device 1 according to the present invention is improved in overall luminance compared to the conventional direct liquid crystal display device (1). That is, among the light incident from the lamp 23a into the second light guide plate 22, light directed toward the plate surface on which the light diffuser 21a of the second light guide plate 22 is formed is diffused through the light diffuser 21a. The light guide plate 21 is incident on the first light guide plate 21, and as shown in FIG. 7, the luminance is improved as compared with the conventional direct type liquid crystal display device 1.

In addition, in the liquid crystal display device 1 according to the present invention, since the lamp 23a is disposed on the side of the light guide plate, the influence of heat generated from the lamp 23a is small. 8 is a view showing a temperature distribution between the liquid crystal display device 1 according to the present invention and a conventional direct liquid crystal display device 1, and FIG. 9 is a time chart of the liquid crystal display device 1 according to the present invention. It is a figure which shows another brightness change. As shown in these figures, in the liquid crystal display device 1 according to the present invention, the influence of heat from the lamp 23a is reduced, so that the decrease in luminance of the liquid crystal display device 1 due to heat can be significantly reduced.

In addition, the liquid crystal display device 1 according to the present invention has a reduced thickness compared to the conventional direct liquid crystal display device 1. That is, in the case of the conventional direct type liquid crystal display device 1, the lamp 23a is disposed behind the liquid crystal display panel 10 so as to prevent bright lines generated due to luminance deviation between the lamps 23a. 23a) and the liquid crystal display panel 10 should be maintained at a predetermined interval or more, but in the case of the liquid crystal display device 1 according to the present invention, a space other than the thicknesses of the first light guide plate 21 and the second light guide plate 22 may be formed. Since there is no need to consider, the thickness can be reduced as compared with the conventional direct type liquid crystal display device 1. In addition, the liquid crystal display device 1 according to the present invention, while reducing the thickness, it is possible to secure a viewing angle equivalent to that of the conventional direct liquid crystal display device 1.

Further, the liquid crystal display device 1 according to the present invention can significantly reduce the manufacturing cost of the liquid crystal display device 1 as compared to the conventional direct type liquid crystal display device while having the above quality improvement. That is, the light diffusion unit provided in the first light guide plate 21 and the second light guide plate 22 without using an expensive ITO sheet used to remove horizontal line noise in the conventional direct type liquid crystal display device 1 By 21a) it is not necessary to use a separate diffusion sheet, the manufacturing cost can be significantly reduced.

As described above, according to the present invention, a backlight assembly capable of reducing the manufacturing cost and reducing the manufacturing cost by reducing the thickness of the liquid crystal panel while reducing the thickness thereof, and reducing the manufacturing cost, using the same A liquid crystal display device is provided.

Claims (11)

A liquid crystal display panel on which an image is displayed; A printed circuit board driving the liquid crystal display panel; A backlight assembly having a plurality of light guide plates disposed behind the liquid crystal display panel at mutually spaced intervals, and a lighting unit disposed in at least one area around edges of the light guide plates to illuminate the light guide plates; And a flexible printed circuit board interconnecting the liquid crystal display panel and the printed circuit board and bent along an edge region of the backlight assembly such that the printed circuit board is disposed at an area around an edge of the backlight assembly. Liquid crystal display device. The method of claim 1, The backlight assembly may further include a spacer disposed between the plurality of light guide plates such that the plurality of light guide plates are spaced apart from each other. The method of claim 1, The backlight assembly may further include a support frame surrounding the lighting unit in a plate direction outer side of the light guide plate. The method of claim 1, The backlight assembly may further include a reflecting plate disposed at a rear side of the plurality of light guide plates to reflect the light. The method of claim 2, The backlight assembly may further include an auxiliary reflector disposed between the spacer and the light guide plates to reflect light. The method of claim 5, And the stopper is provided at the separation part to prevent the auxiliary reflector from moving inward along the plate surface direction of the light guide plate. The method of claim 1, And the backlight assembly further comprises light diffusing parts provided on surfaces of the light guide plates facing each other. The method of claim 7, wherein Wherein each of the light diffusing portions is a concave-convex pattern formed on a plate surface of each of the light guide plates. The method of claim 1, And a front frame interposed between the liquid crystal display panel and the light guide plate disposed at the foremost of the plurality of light guide plates. The method of claim 1, The backlight assembly may further include a light diffusion part provided in at least one region of the front or rear surface of the light guide plate. The method of claim 10, And the light diffusing portion is a concave-convex pattern formed on a plate surface of the light guide plate.