KR100683746B1 - Chassis assembly for plasma display apparatus and plasma display apparatus comprising the same - Google Patents

Abstract

An object of the present invention is to provide a chassis assembly for a plasma display device having a structure in which a discharge delay phenomenon is reduced, and a plasma display device having the same. To achieve this object, the present invention has a thermal conductivity of 10 W / mK to 100 W. A chassis assembly for a plasma display device having a chassis of / mK and a plasma display device having the same are provided.

Description

Chassis assembly for plasma display device and plasma display panel having same {Chassis assembly for plasma display apparatus and plasma display apparatus comprising the same}

1 is a graph illustrating a discharge delay of a plasma display device.

2 is an exploded perspective view of a plasma display device according to an embodiment of the present invention.

FIG. 3 is a partially cutaway perspective view illustrating an example of the plasma display panel illustrated in FIG. 2.

4 is a graph showing a relationship between an address voltage and a discharge current over time.

5 is a graph showing the relationship between the thermal conductivity and the delay time of the chassis.

Explanation of symbols on the main parts of the drawings

200: plasma display device 210: plasma display panel

220: chassis 223: double-sided tape

227: heat conductive sheet 230: circuit portion

240: boss 250: reinforcing member

260: cover plate 271: TCP

275 electronic device

The present invention relates to a chassis assembly for a plasma display device and a plasma display device, and more particularly, to a chassis assembly for a plasma display device having a structure in which a discharge delay phenomenon is reduced, and a plasma display device having the same.

Plasma display device is a flat panel display device that realizes images by using gas discharge phenomenon. It has large screen, high quality, ultra thin, light weight and wide viewing angle, and it is simpler to manufacture than other flat panel display devices. Due to its ease of size, it has recently been in the spotlight as a large flat panel display.

Since the plasma display panel uses a driving principle in which an image is displayed by internal gas discharge, a large amount of heat is generated when driving the plasma display panel. If the heat generated in the plasma display panel is not properly discharged to the outside, the afterimage occurs in the plasma display panel. Therefore, in order to prevent such an afterimage problem, heat generated in the plasma display panel is generally discharged to the outside through the chassis disposed on the rear surface of the plasma display panel. In general, the chassis is made of aluminum having a high thermal conductivity, the thermal conductivity of the aluminum is about 150W / mK to 220W / mK.

As such, when the chassis is manufactured using a material having a high thermal conductivity, there is an advantage in heat dissipation ability. However, when the temperature of the place where the plasma display panel is disposed decreases, the temperature of the discharge gas charged in the discharge cells of the plasma display panel is lowered, thereby causing a plasma discharge delay in the plasma display panel. Here, the discharge delay does not occur during the time period when the plasma discharge is required in the discharge cell, but means that the discharge is delayed.

1 schematically shows a discharge delay phenomenon. In the graph of FIG. 1, the horizontal axis represents time and the vertical axis represents the magnitude of the discharge current. Referring to the drawing, the discharge current required in one discharge cell is the first curve G1. However, when a discharge delay occurs, the discharge current has a second curve G2, and the discharge current is delayed by a predetermined time Δt. As described above, the discharge delay is increased as the heat radiation of the plasma display panel is excessively generated and the temperature of the discharge gas charged in the discharge cells decreases.

In order to solve the above problems, an object of the present invention is to provide a chassis assembly for a plasma display device having a structure in which a discharge delay phenomenon is reduced and a plasma display device having the same.

In order to achieve the above object and other objects, the present invention provides a chassis assembly for a plasma display device having a chassis having a thermal conductivity of 10W / mK to 100W / mK.

According to another aspect of the present invention, the present invention provides a plasma display panel for displaying an image using a gas discharge, and a plasma display device supporting the plasma display panel, the chassis having a thermal conductivity of 10W / mK to 100W / mK To provide.

In the present invention, it is preferable that the thermal conductivity of the chassis is 50 W / mK to 100 W / mK.

In the present invention, preferably, the chassis is formed of a material containing iron (iron). In this case, the chassis is preferably formed of a material containing galvanized iron (galvanized iron).

In the present invention, the thickness of the chassis is preferably 0.8 mm to 2.0 mm.

In the present invention, preferably, the chassis assembly or the plasma display apparatus may further include a reinforcing member disposed on one side of the chassis and reinforcing rigidity of the chassis. At this time, the reinforcing member is preferably formed using the same material as the chassis.

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is an exploded perspective view of the plasma display apparatus 200 according to an exemplary embodiment of the present invention. Referring to FIG. 2, the plasma display apparatus 200 includes a chassis assembly including a chassis 220 and reinforcing members 250 and a plasma display supported in front of the chassis 220 to implement an image using gas discharge. And a circuit unit 230 supported at the rear of the panel 210 and driving the plasma display panel 210.

3 is a partial cutaway perspective view of the AC three-electrode surface discharge plasma display 210 as an example of the plasma display panel illustrated in FIG. 2. As shown, the plasma display panel 210 includes an upper plate 211 and a lower plate 212 coupled in parallel thereto. The sustain electrode pairs 12 are disposed on the front substrate 11 of the upper plate 211. At this time, since the image is projected through the front substrate 11, the front substrate 11 is preferably formed of a transparent material mainly composed of glass. The sustain electrode pair 12 means a pair of sustain electrodes 31 and 32 formed on the front substrate 11 to cause sustain discharge, and the sustain electrode pair 12 is attached to the front substrate 11. Are arranged in parallel at predetermined intervals. Each sustain electrode pair 12 includes a scan electrode 31 and a common electrode 32. In addition, each of the scan electrode 31 and the common electrode 32 includes transparent electrodes 31a and 32a and bus electrodes 31b and 32b. The transparent electrodes 31a and 32a are formed of a transparent material which is a conductor capable of causing a discharge and does not prevent the light emitted from the phosphor layer 26 from advancing to the front substrate 11. tin oxide). However, transparent conductors such as ITO generally have high resistance, and thus, when the discharge sustaining electrode is formed only by the transparent electrode, the voltage drop in the longitudinal direction is large, so that driving power is consumed and the response speed is slow. In order to improve this, bus electrodes 31b and 32b made of a metal material and formed in a narrow width are disposed at the outer end of the transparent electrode. On the rear substrate 21 opposite to the front substrate 11, the address electrodes 22 are disposed to intersect the scan electrode 31 and the common electrode 32 in the unit discharge cell 70. The address electrodes 22 are used to generate an address discharge for facilitating sustain discharge between the scan electrode 31 and the common electrode 32. More specifically, the address electrodes 22 lower the voltage for sustain discharge. The address discharge is a discharge occurring between the scan electrode 31 and the address electrode 32. When the address discharge is completed, cations are accumulated on the scan electrode 31 side and electrons are accumulated on the common electrode side, thereby scanning electrode 31. Sustain discharge between the common electrode 32 and the common electrode 32 becomes easier. The space formed by the pair of scanning electrodes 31 and the common electrode 32 and the address electrodes 22 intersecting the same forms a single discharge unit as the unit discharge cells 70. The front dielectric layer 15 is formed on the front substrate 11 to fill the sustain electrode pair 12. The front dielectric layer 15 is directly energized between the scan electrode 31 and the common electrode 32 adjacent to the kitchen and damages the sustain electrodes 31 and 32 by directly impinging cations or electrons on the electrodes 31 and 32. It is possible to induce charge and to accumulate wall charges while preventing light from being formed, and is formed as a dielectric having good light transmittance. Such dielectrics include PbO, B ₂ O ₃ and SiO ₂ . In addition, a protective layer 16 usually made of MgO is formed on the front dielectric layer 15. The protective layer 16 prevents cations and electrons from colliding with the front dielectric layer 15 during discharge, thereby damaging the front dielectric layer 15, having good light transmittance, and emitting a large amount of secondary electrons during discharge. The back dielectric layer 25 is formed on the back substrate 21 so as to fill the address electrode 22. The back dielectric layer 25 is formed as a dielectric that can induce charge while preventing cations or electrons from colliding with the address electrode 22 during discharge and damaging the address electrode 22. Such dielectrics include PbO and B _2. O ₃ , SiO ₂ and the like. On the back dielectric layer 25, barrier ribs 30 are formed to maintain a discharge distance and prevent electro-optical crosstalk between discharge cells. Red, green, and blue light emitting phosphor layers 26 are coated on both sides of the barrier ribs 30 and the front surface of the back dielectric layer 25 in which the barrier ribs 30 are not formed. 3 illustrates a matrix-type partition wall 30 that partitions the discharge cells 70 having a rectangular cross section, but is not limited thereto.

Referring to the operation of the plasma panel 210 according to the present invention configured as described above are as follows. Hereinafter, the driving of the plasma display panel using the address-display separation (ADS) driving method will be described. However, the present invention is not limited thereto.

The plasma discharge generated in the plasma display panel 210 is largely divided into address discharge and sustain discharge. The address discharge is caused by the application of the address discharge voltage between the address electrode 22 and the scan electrode 32, and as a result of the address discharge, the discharge cell 180 in which the sustain discharge occurs is selected. In more detail, the scan pulse is applied to the scan electrode and the address pulse is applied to the address electrode 122, thereby maintaining the address discharge voltage between the address electrode and the scan electrode. Thereafter, when a sustain voltage is alternately applied between the scan electrode 31 and the common electrode 32 of the selected discharge cell 70, particles such as electrons accumulated in the scan electrode 31 and the common electrode 32 are accumulated. It collides to generate sustain discharge, and the energy level of the discharged gas excited during the sustain discharge is lowered to emit ultraviolet rays. The ultraviolet rays excite the phosphors 26 applied in the discharge cells 70. As the energy level of the excited phosphors 26 decreases, visible light is emitted, and the emitted visible light forms an image.

When the plasma display panel 210 is driven as described above, a lot of heat is generated by the plasma discharge. If the generated heat is not properly discharged to the outside, an afterimage may occur in the plasma display panel 210. Therefore, the chassis 220, which not only serves to structurally support the plasma display panel 210 but also serves as a heat radiating member, is disposed behind the plasma display panel 210. The thickness of the chassis may be variously selected in consideration of the size of the plasma display panel and the like. However, in order to reduce thickness and weight, the thickness of the chassis is preferably 0.8 mm to 2.0 mm.

In addition, a thermal conductive medium 227 is interposed between the plasma display panel 210 and the chassis 220. The heat conducting medium 227 not only removes local heat concentration by dispersing heat generated from the plasma display panel 210, but also transmits heat generated from the plasma display panel 210 to the chassis 220. do. In this embodiment, the heat conducting medium 227 has a shape of a single sheet, one side is attached to the plasma display panel 210, the other side is attached to the chassis 220 is preferable for heat dissipation. However, the shape and interposition method of the thermally conductive medium 227 is not limited to the above, and may be disposed separately into a plurality of sheets, and may be disposed to be spaced apart between the thermally conductive medium and the chassis. In order to improve thermal conductivity, the thermal conductive medium 227 may be formed of carbon-based or silicon such as graphite having high thermal conductivity.

In the present embodiment, the plasma display panel 210 and the chassis 220 are joined by double-sided tapes 223 interposed between them 210 and 220, and the double-sided tapes 223 are a single sheet of thermal conductive medium ( 227 is arranged to surround.

The circuit unit 230 for driving the plasma display panel 210 is installed to be spaced apart from the rear surface of the chassis 220 by the bosses 240. In general, the bosses 240 formed in the chassis 220 and the screw inserted into the through-holes of the circuit unit 230 are coupled to each other.

Signal transmission means connects them 210 and 230 to transmit electrical signals and power between the plasma display panel 210 and the circuit unit 230. In this embodiment, a flexible printed circuit (FPC) 272 and a tape carrier package (hereinafter referred to as "TCP") 271 are adopted as signal transmission means. In particular, the TCP 271 is connected between the address driver of the circuit unit 230 and the address electrodes 22 of the plasma display panel, and the cover plate 260 is provided on the TCP 271 on which the electronic device 275 is mounted. Disposed to dissipate heat generated from the electronic element 275 to the outside. A heat conductive sheet (not shown) is inserted between the TCP 271 and the cover plate 260, and heat transfer is promoted between the TCP 271 and the reinforcing member 250 and applied to the electronic element 275. Grease (not shown) is inserted to relieve the compressive force.

The reinforcement member 250 is disposed on the rear surface of the chassis 220 to reinforce the strength of the chassis 220. The reinforcement member 250 is fixed to the chassis 220 by screws (not shown). The reinforcing members 250 are not overlapped with the circuit portion 230 and are disposed at portions that do not interfere with the circuit connection between the circuit portions 230. Reinforcement member 250 has a variety of cross-section "b" or "c" shape. The reinforcement member 250 may be manufactured and coupled separately from the chassis 220, but in order to reduce the manufacturing process, the chassis 220 and the reinforcement member 250 may be integrally formed. In addition, the chassis 220 and the reinforcing member 250 is preferably formed of the same material in order to prevent bending due to different thermal expansion coefficients between the reinforcing member 250 and the chassis 220.

As described above, when the plasma display panel 210 radiates heat while the plasma display panel 210 is driven, the discharge delay phenomenon occurs in the plasma display panel. That is, the discharge in the discharge cells 70 is not made at the desired time period, but is discharged later than the desired time. Therefore, the chassis 220 should be formed of a material capable of maintaining rigidity and appropriately maintaining the internal temperature of the plasma display panel 210.

When the plasma display panel 210 is driven, the discharge delay is largely generated in the address discharge period and the sustain discharge period. In the sustain discharge section, however, a plurality of sustain discharge pulses are applied to the electrodes 31 and 32 disposed in the one discharge cell 70, while the scan electrode 32 and the address electrode of the one discharge cell are applied in the address discharge section. Since one scan pulse and one address pulse are applied to 22, the discharge delay shape occurring in the address discharge period becomes a larger problem than the discharge delay occurring in the sustain discharge period.

4 schematically shows a relationship between the voltage G3 of the address electrode and the discharge current G4 over time in one address pulse applied to the address electrode 22 in the address discharge period. The horizontal axis of the graph of FIG. 4 represents a time axis in nanosecond units, the left vertical axis Y1 represents an address voltage, and the right vertical axis Y2 represents a discharge current.

As shown in the graph of FIG. 4, as the voltage of the address electrode increases from the first time t1 to the second time t2, after the voltage increases from the first voltage V1 to the second voltage V2. In the second time t2, the third time t2 is maintained at a constant voltage V2 = V3. After that, the voltage is decreased to recover to the fourth voltage V4 having the same magnitude as the initial voltage at the fourth time t4.

The time of one pulse applied to the address electrode, that is, the time interval from the first time t1 to the fourth time t4 is 1000 ms. At this time, the interval between the first time t1 and the second time t2 is 200 ms, and the interval between the second time t2 and the third time t3 is 650 ms, the third time t3 and the fourth time. The interval between time t4 is 150 ms.

During address discharge, the discharge current occurs at the first discharge time s1, has a maximum value at the second discharge time s2, and disappears at the third discharge time s3, and the magnitude of the discharge current has a convex parabolic shape. Have In addition, the duration of the discharge current is generated for about 350 mA between the first discharge time s1 and the third discharge time s3.

For stable address discharge, the discharge current G4 is located between the second time t2 and the third time t3. Therefore, about 650 kHz for the generation of visible light should be secured during 650 kHz between the second time t2 and the third time t3. That is, since the discharge should be generated within the time of subtracting 350 mA, which is the discharge current duration time, out of the 650 mA between the second time t2 and the third time t3, the discharge delay time should be maintained at 300 ms or less. From this consideration, the material of the chassis 220 should be selected such that the time ΔD between the first discharge time s1 and the second time t2 is kept below 300 ms. Hereinafter, the time ΔD between the first discharge time s1 and the second time t2 is defined as a delay time for convenience.

Table 1 is an experimental result of measuring the delay time ΔD by changing the thermal conductivity of the chassis 220, and FIG. 5 is a graph showing the experimental values of Table 1. FIG. The experiment was performed by installing a 42-inch plasma display panel 210 in a chamber having a temperature of −30 ° C., wherein the chassis 220 had a thickness of 2 mm and the thermal conductive medium 227 had a thickness of 1.4 mm. Carbon sheet was used. Experimental values were measured when the plasma display panel 210 was operating in a steady state.

Thermal Conductivity (W / mK) 0.02 7 10 15 50 75 100 150 200 Delay time (㎱) -60 -50 100 120 150 160 175 320 460

As shown, it can be seen that the delay time ΔD increases as the thermal conductivity of the chassis 220 increases. When the thermal conductivity of the chassis 220 is increased, since the heat radiation from the plasma display panel 210 is promoted and the temperature of the plasma display panel 210 is kept low, the delay time ΔD is increased. In this case, the negative delay time ΔD indicates that the first discharge time s1 occurs earlier than the second time t2, and in this case, the plasma display panel 210 causes overdischarge. Overdischarge occurs because the heat generated in the plasma display panel is not effectively released when the thermal conductivity of the chassis is too low, so that the internal temperature of the plasma display panel rises above an appropriate value.

Referring to FIG. 5, since the time ΔD between the first discharge time s1 and the second time t2 should be maintained at 0 to 300 mW, the thermal conductivity of the chassis 220 is preferably 100 W / mK or less. . In particular, when the thermal conductivity of the chassis 220 exceeds 100W / mK, since the delay time DELTA D increases rapidly, it is difficult to obtain desirable discharge characteristics of the plasma display panel. In addition, in order to prevent overdischarge of the plasma display panel 210, since the delay time DELTA D should be 0 ms or more, the thermal conductivity of the chassis 220 is preferably 10 W / mK or more. Therefore, in order to prevent the occurrence of discharge delay and overdischarge, the thermal conductivity of the chassis 220 is preferably 10W / mK to 100W / mK. However, since the delay time ΔD has relatively similar values at 50 W / mK to 100 W / mK, the thermal conductivity of the chassis 220 is more preferably 50 W / mK to 100 W / mK for plasma discharge stability.

In particular, when the chassis 220 is formed of an electro-galvanized steel sheet having a thermal conductivity of about 65 W / mK in the above experiment, the temperature measured at the portion adjacent to the TCP 271 is about less than that of a chassis made of general aluminum. It was measured to increase by 10 ° C. This proves that chassis made of materials with low thermal conductivity maintain high temperatures throughout.

The material having a thermal conductivity of 10 W / mK to 100 W / mK or less may be selected in various ways. It is preferable that the material be formed of a material including iron in rigidity and cost. In particular, the material containing iron is preferably formed of a material containing a galvanized steel sheet to prevent corrosion. At this time, the galvanizing can be carried out in a variety of ways, preferably considering the cost and ease of manufacture, electrolytic galvanized iron or hot dip galvanized iron (hot dip galvanized iron) using an electrical method It is preferable to manufacture the chassis 220 from the material containing. In the case of a galvanized steel sheet, the thermal conductivity is about 65 W / mK. Thus, the plasma display panel has a proper thermal conductivity when the plasma display panel is driven at a high temperature as well as at a low temperature, and is a material having safety in environmental hazards. In particular, in the case of hot-dip galvanized steel sheet, since the thickness of the galvanized layer is thick, it has good characteristics in preventing corrosion.

In addition, when the chassis 220 is formed using the galvanized steel sheet, vibration and noise of the plasma display apparatus 200 are reduced. This will be described in more detail as follows.

Since the plasma display panel 210 performs plasma discharge, vibration and noise generated during discharge are transmitted to the chassis 220, and the vibration and noise are secondarily harmonized with electromagnetic noise characteristics of the circuit unit 230. It is amplified. If noise above an appropriate value is generated, it is a dissatisfaction factor of the user, so a noise reduction method of the plasma display panel should be devised.

However, the noise generated by the vibration and electromagnetic characteristics may be expressed as acoustic energy, and in order to reduce the noise, the noise may be reduced by converting the acoustic energy into another form of energy. As a representative example for reducing noise, sound absorbing materials for converting acoustic energy into thermal energy are used, but vibration and noise generated in the plasma display panel 210 are transmitted to the chassis 220 made of a material having a high density. Noise can be reduced by reducing energy.

In general, the transmission loss of noise according to the surface density of the medium and the natural frequency may be represented by the following Equation 1. Referring to Equation 1, as the density of the medium material increases, the transmission loss increases, so that the transmission of noise and vibration is reduced, and as a result, the noise through the medium is reduced.

TL = 18 log mf-44 [dB]

m: surface density of the medium [kg / m 2]

f: frequency [Hz]

Based on the above theoretical basis, the noise of the plasma display apparatus 200 was measured by changing the material of the chassis 220. In the noise measurement according to the chassis, the SPL value was measured using a microphone sensor at a predetermined distance from the front and rear surfaces of the display device, and the results compared with the conventional aluminum chassis are shown in Table 1. In this experiment, the noise values in the chassis formed using a conventional aluminum and the chassis formed of an electrogalvanized steel sheet applied in one embodiment of the present invention was compared and measured. Referring to Table 2, it can be confirmed that the noise is reduced in the chassis formed of the galvanized steel sheet, because the surface density of the galvanized steel sheet is large, the transmission loss of the noise is large.

aluminum Electro Galvanized Steel Sheet Remarks  Front (dB)  26.3  25.3 Average of five experimental values  Rear (dB)  31.5  27.8

However, in the present invention, as well as galvanized steel sheet containing iron, the chassis can be manufactured using a variety of materials. Table 3 shows the thermal conductivity of the three aluminum alloys usable in the present invention. It can be seen that all three have thermal conductivity of 10 W / mK to 100 W / mK. In addition, Table 4 shows the thermal conductivity of low carbon steel, medium carbon steel and high carbon steel usable in the present invention. However, the aluminum alloy and carbon steel used in the chassis of the present invention is not limited to the aluminum alloy and carbon steel listed in Tables 1 and 2. In addition, the chassis 220 uses a variety of materials and composites thereof, including stainless steel, aluminum oxide, carbon silicon, titanium, zirconium, copper, cobalt, palladium, carbon fiber, graphite fiber, glass fiber, and the like. Can be formed.

[Table 3] Thermal conductivity according to aluminum alloy

designation Thermal Conductivity (W / mK) MMCC Al / Al ₂ O ₃ (Continuous Fiber Aluminum Matrix Composite) 80 MMCC Al / Al ₂ O ₃ (Short Fiber Aluminum Matrix Composite) 100 MMCC Al / Al ₂ O ₃ (Particulate Aluminum Matrix Composite) 55

[Table 4] Thermal conductivity according to the type of carbon steel

Iron content (% by weight) Carbon content (wt%) Thermal Conductivity (W / mK) Low carbon steel 99.11-99.56 0.14-0.23 51.9 Medium carbon steel 98.46-99.13 0.27-0.55 51.9 High carbon steel 98.38-98.95 0.55-1.03 46.6

In the plasma display device according to the present invention, since the plasma display panel is operated within an appropriate temperature range by a chassis having a thermal conductivity of 10 W / mK to 100 W / mK, the discharge delay phenomenon of the plasma display panel is suppressed. In addition, overdischarge of the plasma display panel is prevented.

In particular, when the chassis is formed of a galvanized steel sheet, not only can the cost be reduced, but the rigidity is excellent, and the noise is reduced.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (25)

A chassis assembly for a plasma display device comprising a chassis comprising at least one material selected from the group consisting of galvanized steel, MMCC Al / Al2O3, or carbon steel. delete delete delete The method of claim 1, And said chassis is formed of a material comprising an electrolytic galvanized iron. The method of claim 1, And the chassis is formed of a material including a hot dip galvanized iron. The method of claim 1, Chassis assembly for a plasma display device, characterized in that the thickness of the chassis is 0.8mm to 2.0mm. The method of claim 1, And a reinforcing member disposed on one side of the chassis, the reinforcing member reinforcing rigidity of the chassis. The method of claim 8, And the chassis and the reinforcing member are integral. The method of claim 8, And the chassis and the reinforcement member are formed of the same material. A plasma display panel which displays an image using gas discharge; And And a chassis supporting the plasma display panel, the chassis including at least one material selected from the group consisting of a galvanized steel sheet, MMCC Al / Al2O3, or carbon steel. delete delete delete The method of claim 11, And the chassis is formed of a material including an electrogalvanized steel sheet. The method of claim 11, And the chassis is formed of a material including a hot-dip galvanized steel sheet. The method of claim 11, The thickness of the chassis is a plasma display device, characterized in that 0.8mm to 2.0mm. The method of claim 11, And a heat conducting medium interposed between the plasma display panel and the chassis. The method of claim 18, And the thermally conductive medium is formed of a carbon-based or silicon-containing material. The method of claim 18, And one surface of the thermally conductive medium is attached to the plasma display panel. The method of claim 18, And one surface of the thermally conductive medium is attached to the chassis. The method of claim 18, And said thermally conductive medium is a single sheet. The method of claim 11, And a reinforcing member disposed on one side of the chassis and reinforcing rigidity of the chassis. The method of claim 23, wherein And the chassis and the reinforcing member are integrated. The method of claim 23, wherein And the chassis and the reinforcing member are made of the same material.

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