KR100982387B1 - Bottom chassis for thin film transistor liquid crystal display device - Google Patents

Abstract

A bottom chassis for housing a backlight unit of a thin film transistor type liquid crystal display device and a method of manufacturing the same will be described.

The bottom chassis for a thin film transistor type liquid crystal display device according to the present invention is carbon (C): 0.001 to 0.1% by weight, silicon (Si): 0.002 to 0.05% by weight, manganese (Mn): 0.28 to 2.0% by weight, chromium ( Cr): 0.01 to 0.03% by weight, molybdenum (Mo): 0.001 to 0.004% by weight and an inner layer formed of a high tensile strength steel sheet containing residual iron (Fe) and other unavoidable impurities; An electrogalvanized layer formed on the inner layer; And a polymer chromium free antifouling layer formed on the electro zinc plating layer, wherein the inner layer, the electro zinc plating layer, and the entire chromium free antifouling layer are 0.5 to 0.9 mm in thickness.

The bottom chassis for a thin film transistor type liquid crystal display device according to the present invention has a relatively thin thickness compared to a conventional bottom chassis to achieve light weight and slimness, and an anti-pollution layer is formed on an outer surface of the operator during product assembly. It has contamination resistance to fingerprints and contaminants, and does not contain chromium, which does not adversely affect the environment.

Description

Bottom chassis for thin film transistor type liquid crystal display device and manufacturing method thereof {Bottom chassis for thin film transistor liquid crystal display device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom chassis for a TFT-LCD and a method of manufacturing the same. More particularly, the present invention relates to a backlight unit that is essentially included in a thin film transistor type liquid crystal display. In manufacturing a bottom chassis for accommodating the same, the present invention relates to a technology capable of achieving a lighter weight and a slimmer bottom chassis, and imparting contamination resistance.

A thin film transistor type liquid crystal display device (TFT-LCD) is a type of flat panel display, and uses a method of controlling the change of liquid crystal and the amount of light passing through the polarizer. TFT-LCD is used as a display of many devices such as monitors, mobile phones, televisions and digital cameras of notebook computers and desktop computers due to the low power consumption, light weight and thinness, and high resolution.

The TFT-LCD is largely composed of a panel unit, a back light unit, and a bottom chassis.

Among them, the bottom chassis serves to store and support the backlight unit and to radiate heat generated from the light source. In some cases, the bottom chassis serves as a grounding role of the light source and a shielding of electromagnetic waves. Such a bottom chassis is required to have strength, surface electrical conductivity, chemical resistance, and excellent workability.

On the other hand, the conventional bottom chassis is mainly used a steel sheet (Steel Sheet), the strength is not good when the thickness of the steel sheet is thin, mainly complemented the strength by using a relatively thick steel sheet of 1mm or more. Accordingly, the weight and thickness of the bottom chassis have a relatively large value, and there is a problem in that the overall weight and thickness of the TFT-LCD are limited. In addition, the conventional bottom chassis is vulnerable to fingerprints or contaminants of the operator during the TFT-LCD assembly process.

Accordingly, the thin film transistor type liquid crystal display device (TFT) may be lighter and thinner than 0.9mm in thickness while maintaining high strength, and may have stain resistance against fingerprints or contaminants in the TFT-LCD assembly process. Bottom chassis for LCD) is required.

SUMMARY OF THE INVENTION An object of the present invention is a bottom chassis for storing a back light unit, which is essentially included together with a panel unit, in a thin film transistor type liquid crystal display device (TFT-LCD). The present invention provides a bottom chassis for a thin film transistor type liquid crystal display device that can be lighter and slimmer as a whole in a TFT-LCD while providing strength resistance to the bottom chassis while maintaining strength, and at the same time, making it lighter and slimmer than a conventional bottom chassis.

Bottom chassis for a thin film transistor type liquid crystal display device according to an embodiment of the present invention for achieving the above object is carbon (C): 0.001 ~ 0.1% by weight, silicon (Si): 0.002 ~ 0.05% by weight, manganese (Mn) : 0.28 to 2.0% by weight, chromium (Cr): 0.01 to 0.03% by weight, molybdenum (Mo): 0.001 to 0.004% by weight, and an inner layer formed of a high tensile strength steel sheet containing residual iron (Fe) and other unavoidable impurities; An electrogalvanized layer formed on the inner layer; And a polymer chromium free antifouling layer formed on the electro zinc plating layer, wherein the inner layer, the electro zinc plating layer, and the entire chromium free antifouling layer are 0.5 to 0.9 mm in thickness.

At this time, the polymer chromium free anti-fouling layer is 10-30% by weight of the amine resin, in the one or more kinds of glycidoxy propyl ethoxysilane, aminopropyl ethoxysilane, methoxyoxypropyl drimethoxysilane selected from colloidal silica or fumed silica 1 to 10% by weight of the silica compound mixed at a ratio of 1 or more selected by weight 1: 0.2 to 0.8, at least one inorganic sol of zirconia sol, alumina sol and titanium sol, and the balance of the epoxy resin You can present what is included.

On the other hand, the bottom chassis manufacturing method for a thin film transistor type liquid crystal display device according to the present invention (a) carbon (C): 0.001 to 0.1% by weight, silicon (Si): 0.002 to 0.05% by weight, manganese (Mn): 0.28 ~ Electro galvanized on an inner layer formed of a high tensile strength steel sheet containing 2.0% by weight, chromium (Cr): 0.01 to 0.03% by weight, molybdenum (Mo): 0.001 to 0.004% by weight and residual iron (Fe) and other unavoidable impurities. Performing to form an electrogalvanized layer; And (b) a polymer chromium free composed of an epoxy resin as a solid resin in an amount of 10 to 30% by weight of an amine resin, 10 to 50% by weight of a silica mixture, 1 to 10% by weight of an inorganic sol and a residual binder resin on the surface of the electrogalvanized layer. Coating an antifouling composition to form a polymer chromium free antifouling layer.

The bottom chassis for a thin film transistor type liquid crystal display device according to the present invention has the effect of being lightweight and slim, and also has a high strength even though it is thinner than the conventional one, and during the product assembly process through the polymer chromium-free fouling layer. It has contamination resistance to fingerprints or contaminants of workers, and does not contain chromium and thus does not adversely affect the environment.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and those skilled in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a bottom chassis for a thin film transistor type liquid crystal display device and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

1 is a schematic exploded perspective view of a thin film transistor type liquid crystal display device.

Referring to FIG. 1, the thin film transistor type liquid crystal display device includes a panel unit 110, a backlight unit 120, and a bottom chassis 130.

The panel unit 110 displays a planar image by using light emitted from the backlight unit 120. The panel unit 110 includes a rear glass substrate (also referred to as a TFT substrate) on which a thin film transistor is formed, and a front glass substrate on which a color filter is formed on a surface facing the rear glass substrate (also referred to as a color filter substrate). And a liquid crystal filled between the two glass substrates. The thin film transistor formed on the rear glass substrate controls the liquid crystal and controls the pixel which is the minimum unit constituting the screen. The color filter formed on the front glass substrate is formed by coating pixels having three colors such as red (R), green (G), and blue (B) on the glass substrate to realize an image.

The backlight unit 120 irradiates light from the rear surface of the panel unit 110. The backlight unit 120 includes a light source, a reflecting plate, an optical plate such as a light guide plate or a diffusion plate, various optical sheets, and the like, and arranges a light source under the panel unit according to the position of the light source to directly illuminate the front of the panel. It is divided into a direct type and an edge type in which a light source is placed at the edge of the panel unit to directly illuminate the front of the panel.

The bottom chassis 130 accommodates the backlight unit 120. In the present invention, the bottom chassis 130 is electro-galvanized on the outer surface of the inner substrate, and a polymer chromium free antifouling layer is formed thereon. In addition to the direct and indirect storage of the backlight unit 120, the bottom chassis 130 may be electrically connected to the light source and other internal circuits of the backlight unit 120 to serve as a ground.

In addition, the TFT-LCD protects the panel unit 110 and the backlight unit 120 from the outside, and fixes the panel unit 110 to the backlight unit 120 to prevent the panel unit 110 from detaching. 140). The top chassis 140 has a form surrounding the edges and sides of the front surface of the panel unit 110.

Figure 2 schematically shows the thickness direction cross section of the bottom chassis according to the present invention. The bottom chassis actually applied to the thin film transistor type liquid crystal display device is manufactured by forming and processing a steel sheet having a cross-sectional structure as shown in FIG.

The bottom chassis 130 includes an inner layer 210 positioned on the side where the backlight unit is accommodated, an electrogalvanized layer 220 and a polymer chromium free antifouling layer 230 positioned on the opposite side of the backlight unit. .

The inner layer 210 is carbon (C): 0.001-0.1% by weight, silicon (Si): 0.002-0.05% by weight, manganese (Mn): 0.28-2.0% by weight, chromium (Cr): 0.01-0.03% by weight, Molybdenum (Mo): It is formed from high tensile steel sheet containing 0.001 to 0.004% by weight and residual iron (Fe) and other unavoidable impurities.

Carbon (C) is added to secure the strength of the inner layer 210. Carbon is preferably added at 0.001 to 0.1% by weight of the total weight of the inner layer. If the carbon is added less than 0.001% by weight, it is insufficient to secure the strength of the inner layer 210, and if it exceeds 0.1% by weight, weldability and toughness may be degraded.

Silicon (Si) is added to secure strength by solid solution strengthening of the inner layer 210. Silicon is preferably added at 0.002 to 0.05% by weight of the total weight of the inner layer. If the silicon is added less than 0.002% by weight, there is a problem in that the solid-solution strengthening effect of the inner layer 210 is lowered, and when the silicon content exceeds 0.05% by weight, the surface quality is reduced by forming an interfacial oxide layer.

Manganese (Mn) is added to secure the strength and workability of the inner layer (210). Manganese is preferably added at 0.28 to 2.0% by weight of the total weight of the inner layer. If manganese is added in less than 0.28% by weight, it is difficult to secure strength and workability, and when the content of manganese exceeds 2.0% by weight, tissue heterogeneity due to manganese segregation may occur.

Other unavoidable impurities of the inner layer 210 include phosphorous (P): 0.1 wt% or less, sulfur (S): 0.008 wt% or less, nickel (Ni): 0.007-0.015 wt%, aluminum (Al): 0.043-0.045 Wt%, copper (Cu): 0.02 to 0.04 wt%, tin (Sn): 0.0017 to 0.0018 wt%, oxygen (O): 0.004 wt% or less, nitrogen (O): 0.003 wt% or less Niobium (Nb): 0.0075 ~ 0.0083 wt% and titanium (Ti): 0.0306 ~ 0.0310 wt% may be further included as necessary. The reason for the addition of the materials is well known and the detailed description thereof will be omitted.

An electrogalvanized layer 220 is formed on the inner layer 210. The electrogalvanized layer 220 may be plated with an adhesion amount of 10 to 30 g / m ² . As a preferred example, electro-zinc plating may suggest performing plating with a deposition amount of 20 g / m ² in a sulfuric acid bath.

The polymer chromium free antifouling layer 230 is formed by coating the polymer chromium free composition on the electrogalvanized layer 220. In the present invention, the antifouling layer 230 is formed based on the polymer resin, and also does not include chromium (Cr).

The polymer chromium free antifouling layer 230 may include an epoxy resin as 10 to 30 wt% of the amine resin, 10 to 50 wt% of the silica mixture, 1 to 10 wt% of the inorganic sol, and the balance of the binder resin.

The amine resin plays a role of imparting adhesive force by crosslinking. Such amine-based resin is preferably contained in 10 to 30% by weight of the total weight of the fouling-resistant layer 230. When the amine resin is added at less than 10% by weight, the adhesive strength due to crosslinking is insufficient, and when it exceeds 30% by weight, the workability is lowered.

Silica mixtures are added to improve storage stability, adhesion, corrosion resistance and processability. The silica mixture is preferably included in 10 to 50% by weight of the total weight of the fouling-resistant layer 230. If the silica mixture is added at less than 10% by weight, the conductivity is deteriorated, and if it exceeds 50% by weight, the workability is lowered.

The silica mixture may be a mixture of silica and silane in a specific ratio, and specifically, silica and clicsidoxypropyl ethoxysilane, aminopropyl ethoxysilane, and methoxyoxypropyl drier selected from colloidal silica or fumed silica. Among the methoxysilanes, selected silanes may be mixed in a weight ratio of 1: 0.2 to 0.8 (silica: silane). When the silica and the silane are mixed in a weight ratio of less than 1: 0.2, crosslinkability is lowered, and when the amount is mixed in excess of 1: 0.8, workability may be reduced.

Inorganic sol is included to improve adhesion and corrosion resistance. Such inorganic sol may be a zirconia sol, an alumina sol, a titanium sol or the like alone or a mixture of two or more. Inorganic sol is preferably included 1 to 10% by weight of the total weight of the fouling-resistant layer 230. If the inorganic sol is less than 1% by weight, the effect of the inorganic sol may not be obtained. If the inorganic sol is more than 10% by weight, corrosion resistance may be improved.

Epoxy resin acts as a binder resin, forms a dense barrier coating, is resistant to corrosion factors such as salt and oxygen, and has excellent corrosion resistance and chemical resistance because hydroxyl groups in the molecule have excellent adhesion to the substrate.

The polymer chromium free antifouling layer 230 is preferably coated with an adhesion amount of 0.8 ~ 1.3 g / m ² . If the deposition amount is less than 0.8 g / m ² , the workability to the desired bottom chassis shape is lowered. If the deposition amount is more than 1.3 g / m ² , the conductivity is lowered to be included in the light source or element included in the backlight unit 120. There is a problem that can not serve as the ground (Ground) of the circuit. The polymer chromium free antifouling layer 230 coated with the adhesion amount has a thickness of about 1 μm.

The coating of the polymer chromium free antifouling layer 230 coats a solution in which the substances are added to the solvent so that the solid content has the composition on the electrogalvanized layer as a 1 coating 1 baking type, followed by water-cooling after baking. Or cooling by the air cooling system is a preferable example.

The baking drying is preferably carried out in a temperature range of 140 ~ 220 ℃. When baking is carried out at a temperature below 140 ° C., the curing reaction of the resin is not properly performed, and it is difficult to expect the effect of corrosion resistance and other physical properties of the coating layer of the coating film. On the other hand, when baking the baking is carried out at a temperature exceeding 220 ℃, it corresponds to the over-baked portion is likely to cause cracking or yellowing of the coating layer.

The bottom chassis 130 is preferably formed to a thickness of 0.5 ~ 0.9 mm. When the thickness of the bottom chassis 130 exceeds 0.9mm, it is advantageous to form the electrogalvanized layer 220 or the polymer chromium-free contamination prevention layer 230, but the bottom chassis 130, and further, the TFT-LCD light weight and You can't expect to be slim. On the other hand, when the thickness of the bottom chassis 130 is less than 0.5mm, the thickness of the electro-galvanized layer 220 and the polymer chromium-free antifouling layer 230 is so thin that the corrosion, pollution resistance is reduced, or the electro-galvanized layer 220 or Since the thickness of the polymer chromium-free antifouling layer 230 becomes thick, the inner layer 210 itself becomes thin, and thus the strength may be weakened.

3 shows examples of a bottom chassis structure according to the present invention.

The bottom chassis 310 illustrated in FIG. 3A has a structure capable of directly receiving the backlight unit, and the bottom chassis 320 illustrated in FIG. 3B directly supports the backlight unit. Rather than storing, it mainly has a structure of indirectly storing the backlight unit through the role of covering the mold housing the backlight unit.

The bottom chassis for the thin film transistor type liquid crystal display device according to the present invention may be modified into various structures according to the design of the backlight unit of the thin film transistor type liquid crystal display device in addition to the examples shown in FIG. 3.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

1. Manufacturing of steel plate for bottom chassis

Steel sheets according to Examples 1, 2 and Comparative Examples having the compositions shown in Table 1 were prepared, electroplated with a coating weight of 20 g / m ² in a sulfuric acid bath, and coated with a coating of 1 bake on the electroplated layer. The polymer chromium free antifouling layer was coated with an adhesion amount of 1.0 g / m ² , and subjected to baking drying and cooling at 180 ° C. to prepare a steel sheet before forming and processing into a bottom chassis.

TABLE 1

division Example 1 Example 2 Comparative example





adding
element C 0.0013 0.0548 0.0168 Si 0.0029 0.0062 0.0058 Mn 0.3600 0.2810 0.1430 P 0.0678 0.0141 0.0178 S 0.0073 0.0046 0.0044 Cr 0.0297 0.0112 0.0101 Ni 0.0144 0.0073 0.0096 Mo 0.0032 0.0017 0.0022 Al 0.0432 0.0450 0.0375 Cu 0.0351 0.0242 0.0111 Nb 0.0079 - - Ti 0.0308 - - Sn 0.0017 0.0018 0.0014 O 0.0032 0.0038 0.0040 N 0.0015 0.0028 0.0019

2. Mechanical Properties

Table 2 shows the mechanical properties of the steel sheets of Examples 1 and 2 and Comparative Examples prepared above.

TABLE 2

division thickness
(mm) YP
(MPa) TS
(MPa) El
(%) n value r value r-bar Δr Example 1 0.810 215.5 374.3 40.75 0.241 1.76 0.01 Example 2 0.802 221.4 355.4 42.51 0.235 1.67 -0.51 Comparative example 1.002 208.1 327.7 43.26 0.199 1.61 0.80

Referring to Table 2, in Examples 1 and 2, the steel sheet thickness was approximately 0.8 mm, and the yield strength (YP) and tensile strength ( It can be seen that TS) shows a slightly larger value.

3. Moldability Evaluation

In order to evaluate the formability, LDR (Limit Dome Ratio) experiments were performed on the steel sheets manufactured by Examples 1 and 2 and Comparative Examples, and the results are shown in Table 3 below.

[Table 3]

division 108φ 109φ 110φ 111φ 112φ 113φ Example 1 O O O O O X Example 2 O X Comparative example O O O X

In the case of the LDR experiment, the larger the limit value, the better the moldability, and referring to Table 3, it can be seen that Example 1 shows the highest moldability.

4. Workability Evaluation

In order to evaluate the workability, bending experiments were conducted using the 90 ° V bend test method and the 180 ° U bend test method to check whether cracks occurred.

4A and 4B show the results of bending experiments performed by the 90 ° V bend test method and the 180 ° U bend test method in Examples 1-2 and Comparative Examples.

4A and 4B, it can be seen that in Examples 1 and 2 and Comparative Examples, cracks did not occur in the bending test by the 90 ° V bend test method and the 180 ° U bend test method.

5. Other Properties

The corrosion resistance, high temperature, high humidity, conductivity, solvent resistance, alkali resistance, lubricity, cold resistance, and strong alkali corrosion resistance of the steel sheets prepared by Examples 1 and 2 and Comparative Examples were evaluated.

In order to evaluate the corrosion resistance, it was measured whether 1) less than 5% of white blue, 2) peeling off the film by peeling the tape, and 3) whether discoloration (tolerance: good within ΔE≤3).

In order to evaluate high temperature and high humidity, 1) whether there is rust, swelling and precipitate on the surface, 2) discoloration in each case of lamination and lamination (allowable value: within ΔE≤3), 3) peeling off the film by peeling the tape Was measured.

In order to evaluate the conductivity, 1) 10 points were measured at full width and 7 or more were measured to be 1 mΩ or less.

In order to evaluate solvent resistance (MEK), 1) whether or not resin peeling and swelling occurred, and 2) discoloration (acceptable value: ΔE ≦ 1.0) was measured.

In order to evaluate alkali resistance, 1) whether the film was peeled off by peeling the tape and whether color change (acceptable value: ΔE ≦ 0.8) were measured.

In order to evaluate the lubricity, friction coefficient values (good: 0.07 to 0.09) and friction surface blackening or whitening (acceptable value: ΔE ≦ 0.8) were measured.

In order to evaluate cold resistance, it was observed whether white rust and resin melted to reveal a zinc layer.

In order to evaluate strong alkali corrosion resistance, 1) it was observed whether the resin peeling and swelling occurred and whether red blue red.

Table 4 shows the results of the evaluation of the physical properties.

[Table 4]

division Example 1 Example 2 Comparative example Corrosion resistance White and blue Within 5% of white and blue Within 5% of white and blue Within 5% of white and blue Peeling tape clear clear clear ΔE 0.83 1.04 1.06 High temperature and high humidity surface clear clear clear ΔE 1.75 / 1.57 1.75 / 1.49 1.88 / 1.89 Peeling tape clear clear clear conductivity clear clear clear Solvent resistance Resin peeling clear clear clear ΔE 0.35 0.22 0.53 Alkali resistance Peeling tape clear clear clear ΔE 0.30 0.11 0.10 Lubricity Coefficient of friction 0.0840 0.0850 0.0875 ΔE 0.13 0.14 0.29 Cold resistance White and blue clear clear clear Deep discoloration 6 ~ 7mm 6 ~ 7mm 6 ~ 7.5mm Strong alkali
Corrosion resistance Resin peeling
And blue red clear clear clear

Referring to Table 4, it can be seen that in Examples 1 and 2, the corrosion resistance, high temperature and high humidity, conductivity, and the like which are substantially the same as those of the comparative examples used in the related art are exhibited.

As a result, the bottom chassis for a thin film transistor type liquid crystal display device according to the present invention having the above-described physical properties is thinner than the conventional bottom chassis, and has an advantage of showing similar mechanical properties, processability, moldability, corrosion resistance, etc. have. Accordingly, the bottom chassis can be made lighter in weight and slimmer, and thus, the entire thin film transistor type liquid crystal display device can be made lighter and slimmer.

Although the above has been described with reference to one embodiment of the present invention, various changes and modifications can be made at the level of those skilled in the art. Such changes and modifications may belong to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention will be determined by the claims described below.

1 is a schematic exploded perspective view of a thin film transistor type liquid crystal display device.

2 is a schematic cross-sectional view of a bottom chassis of a thin film transistor type liquid crystal display device according to the present invention.

3 shows examples of a bottom chassis structure according to the present invention.

Figures 4a and 4b shows the results of the bending test by the 90 ° V bend test method and 180 ° U bend test method of Examples 1-2 and Comparative Examples.

Claims (14)

In a bottom chassis for storing a backlight unit of a thin film transistor type liquid crystal display device, Carbon (C): 0.001-0.1 wt%, Silicon (Si): 0.002-0.05 wt%, Manganese (Mn): 0.28-2.0 wt%, Chromium (Cr): 0.01-0.03 wt%, Molybdenum (Mo): 0.001 An inner layer formed of a high tensile strength steel sheet containing ˜0.004% by weight and residual iron (Fe) and other unavoidable impurities; An electrogalvanized layer formed on the inner layer; And It is provided with a polymer chromium-free pollution prevention layer formed on the electro zinc plating layer, The thickness of the entire inner layer, the galvanized layer and the chromium-free antifouling layer is a bottom chassis for a thin film transistor type liquid crystal display device, characterized in that the 0.5 ~ 0.9 mm. The method of claim 1, The electro-galvanized layer is a bottom chassis for a thin film transistor type liquid crystal display device, characterized in that the plated with a coating amount of 10 ~ 30 g / m ² . The method of claim 1, The polymer chromium free antifouling layer is a thin film transistor type, characterized in that the epoxy resin is contained as 10 to 30% by weight of the amine resin, 10 to 50% by weight of the silica mixture, 1 to 10% by weight of the inorganic sol and the remaining amount of the binder resin. Bottom chassis for liquid crystal display devices. The method of claim 3, The silica mixture is a thin film, characterized in that the silica selected from colloidal silica or fumed silica and a silane selected from clichy oxypropyl ethoxysilane, aminopropyl ethoxysilane and methoxyoxypropyl drimethoxysilane. Bottom chassis for transistor type liquid crystal display device. The method of claim 4, wherein The bottom chassis for thin film transistor type liquid crystal display device, characterized in that the silica and silane are mixed in a weight ratio of 1: 0.2 ~ 0.8. The method of claim 3, The inorganic sol is a bottom chassis for a thin film transistor type liquid crystal display device, characterized in that at least one of zirconia sol, alumina sol and titanium sol. The method of claim 1, The polymer chromium-free antifouling layer is a bottom chassis for a thin film transistor type liquid crystal display device, characterized in that the coating is coated with an adhesion amount of 0.8 ~ 1.3 g / m ² . The method of claim 1, The inner layer is phosphorus (P): 0.1% by weight or less, sulfur (S): 0.008% by weight or less, nickel (Ni): 0.007-0.015% by weight, aluminum (Al): 0.043-0.045% by weight, copper (Cu) : 0.02 to 0.04% by weight, tin (Sn): 0.0017 to 0.0018% by weight, oxygen (O): 0.004% by weight or less, nitrogen (O): 0.003% by weight or less further comprising a thin film transistor type liquid crystal display Bottom chassis for the device. The method of claim 8, The inner layer is a bottom chassis for a thin film transistor type liquid crystal display device further comprises niobium (Nb): 0.0075 ~ 0.0083 wt% and titanium (Ti): 0.0306 ~ 0.0310 wt%. (a) Carbon (C): 0.001-0.1 wt%, Silicon (Si): 0.002-0.05 wt%, Manganese (Mn): 0.28-2.0 wt%, Chromium (Cr): 0.01-0.03 wt%, Molybdenum (Mo) ): Forming an electrogalvanized layer by electroplating on an inner layer formed of a high tensile strength steel sheet containing 0.001 to 0.004% by weight and residual iron (Fe) and other unavoidable impurities; And (b) Polymer chromium-free contamination consisting of an epoxy resin as a solid resin of 10 to 30% by weight of the amine resin, 10 to 50% by weight of the silica mixture, 1 to 10% by weight of the inorganic sol and the remaining amount of the binder resin on the surface of the electrogalvanized layer. Coating the protective composition to form a polymeric chromium free antifouling layer, A bottom chassis manufacturing method for a thin film transistor type liquid crystal display device, characterized in that the thickness of the entire inner layer, the electro zinc plating layer, and the polymer chromium-free contamination prevention layer is 0.5 to 0.9 mm. The method of claim 10, Step (a) is a bottom chassis manufacturing method for a thin film transistor type liquid crystal display device characterized in that the electroplating is performed in a sulfuric acid bath. The method of claim 10, The step (b) is a bottom chassis manufacturing method for a thin film transistor type liquid crystal display device, characterized in that the coating is made on the electro-galvanized layer in the form of 1 coating 1 baking. The method of claim 10, The method of manufacturing the bottom chassis for a thin film transistor type liquid crystal display device, characterized in that the polymer chromium free antifouling layer of step (b) is formed by baking and drying at 140 to 220 ° C. delete

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