KR100598558B1 - Direct type backlight for clear optical images - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a direct type backlight for obtaining a clear optical image used for manufacturing a back light unit of a TFT-LCD. More particularly, the present invention relates to a diffuser used for a thin film transistor liquid crystal display (TFT-LCD). The present invention relates to a direct-type backlight that obtains a clear light image by inducing uniform light diffusion while passing light emitted from a light source lamp located at a side or a back to obtain a clear image of a display as a sheet. . To this end, according to the present invention, in the direct type backlight capable of obtaining a clear optical image, the adhesive layer 5 adhered between the support 4 and the light diffusing film 1 having the light diffusing layer 3 formed on the base sheet 2 is provided. It characterized in that it comprises a), preferably the refractive index of the adhesive layer 5 is characterized in that the 1.43 ~ 1.59, more preferably the base sheet used in the direct type backlight to obtain the clear optical image The thickness of (2) is characterized by being 10 µm to 150 µm.

Diffusion Sheet, Polyester Film, Support, Umber, Adhesive, Bright Optical Image, Direct Backlight

Description

Direct backlight for clear optical images {REAR TYPE BACKLIGHT UNIT ACQUIRING CLEAR OPTICAL IMAGE}

1 is a cross-sectional view of a part of the direct type backlight to obtain a clear optical image according to the present invention.

Figure 2 is a cross-sectional view of a portion of a conventional direct type backlight.

<Explanation of symbols for main parts of the drawings>

1: Light Diffusion Film 2: Base Sheet

3: light diffusing layer 4: support

5: adhesive layer 6: lamp

7: Normal light 8: Lost light

9. Air layer

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a direct type backlight for obtaining a clear optical image used for manufacturing a back light unit of a TFT-LCD. More particularly, the present invention relates to a diffuser used for a thin film transistor liquid crystal display (TFT-LCD). The present invention relates to a direct-type backlight that obtains a clear light image by inducing uniform light diffusion while passing light emitted from a light source lamp located at a side or a back to obtain a clear image of a display as a sheet. .

In general, the liquid crystal display is a non-light-emitting material, unlike other flat panel display methods, so an additional light emitting device is required to improve the brightness of the display screen. Such light emitting devices include a front light method and a backlight method.

Among them, the backlight method causes the light generated from the light source of the backlight unit attached to the rear side of the display element to the opposite side, and reflects to a reflector such as a metal deposition plate or an opaque white plate so that the light is emitted to the front to display the brightness of the display screen. Indirect lighting method to improve the. In such a backlight method, it is necessary to realize maximum image brightness with a minimum power consumption and a uniform surface light surface. In the case of a computer monitor or a laptop using a display at a short distance, relatively little light emission is required, and a light source is used to convert the light emitted from several lamps into a front light source, but it is used at a long distance and relatively. In the case of a television or a large monitor for which the screen area is also enlarged, a direct backlight is used in which a higher brightness is required and a plurality of lamps are arranged on the rear to satisfy the required brightness.

2 is a cross-sectional view of a part of a conventional direct type backlight. The direct backlight has a frame, a reflective sheet (not shown), and a support placed at a distance from the lamp on the reflective sheet to the front to reduce heat transfer from the lamp to the front and to diffuse the diffusion material used on the front. Increase function. The direct backlight requires high diffusivity to eliminate the bright lines of linear lamps arranged at regular intervals. Such diffusivity imparts a diffusion function by using a diffusion material inside the support material, arranges a diffusion film on the support, or uses both in parallel. A prism sheet or flat reflector film (not shown) may or may not be used on the diffusion film (or light diffusion film).

In the configuration of the conventional direct backlight, the method of disposing the support and the diffusing film is a method of simply disposing each independent material, and the diffusing film that exists independently has a problem that the phenomenon of occurrence of heat is generated by the heat transmitted from the lamp. .

Such a phenomenon occurs by partially varying the distance between the support and the diffusion film to create a light spot of surface light, and in order to minimize this phenomenon, a base film of 150 microns or more is used to cause a decrease in brightness and to thicken the display. In addition, there is a problem in that the light is not transmitted to the front direction by the low refractive index air layer existing between the support and the diffuser film and is lost between the support and the diffuser film so that the brightness of the backlight is lost.

The present invention has been made to solve the above problems, an object of the present invention is to improve the rim phenomenon of the diffusion film to implement a backlight without brightness unevenness, to minimize the light lost by the air layer between the support and the diffusion film In order to improve the brightness of the light and to reduce the thickness of the base film to provide a direct type backlight capable of obtaining a clear optical image.

The direct type backlight capable of obtaining a clear light image according to the present invention for achieving the above object is characterized in that it comprises an adhesive layer bonded between the support and the light diffusion film formed with a light diffusion layer on the base sheet.

Preferably the refractive index of the adhesive layer is 1.43 ~ 1.59.

More preferably, the thickness of the base sheet used in the direct backlight is 10 μm to 150 μm.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples in accordance with the gist of the present invention. .

1 is a cross-sectional view of a part of a direct type backlight capable of obtaining a clear optical image according to the present invention.

Since the base sheet 2 constituting the light diffusion film 1 of the direct backlight can obtain a clear light image according to the present invention, it is necessary to transmit the light emitted from the light source. It is necessary. Synthetic resins used in the base sheet 2 are not particularly limited, but generally include polyethylene telephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, reolefin, cellulose acetate and the like. The base sheet 2 has a thickness of 10 μm to 150 μm, preferably 10 μm to 75 μm. Although the thickness of the base sheet 2, it is not necessary to use a thick substrate due to the characteristics of the light diffusing film 1 according to the present invention to be bonded to the support 4, the light diffusion layer ( 3) It is not possible to facilitate the substrate role of the diffusion layer forming process, such as transferring the diffusion layer structure by the wet coating process or the etching roll to form, on the contrary, the thicker the thickness of the base sheet 2, the liquid crystal display device This is because the luminance of the light emitting device may decrease, and the thickness of the backlight unit may increase, thereby counteracting the demand for thinning the liquid crystal display device.

Elements constituting the base sheet according to the present invention may include organic particles and inorganic particles in addition to the synthetic resin.

In addition, the light diffusion layer 3 according to the present invention is composed of a resin and particles dispersed in the resin, the resin is urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, urethane resin, acrylic resin, Polyurethane, fluorine resin, lycone resin, polyamideimide and the like. In addition to the resin, the light diffusing layer 3 may contain a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, an antifoaming agent, a foaming agent, and the like. Since resin needs to transmit light, transparent resin is preferable, and it is especially preferable that it is colorless and transparent. The particles constituted in the light diffusing layer 3 are substantially spherical particles, and the materials thereof are, for example, acrylic resins, polyurethanes, polyvinyl chlorides, polystyrenes, acrylic copolymers, polystyrene copolymers, polyacrylonitrile, and poly Amide, polymethyl methacrylate, and the like.

The particles are preferably transparent in order to increase the amount of light transmitted through the light diffusing film 1, particularly preferably colorless and transparent. The particle diameter of the particles is preferably 0.1 to 100 µm, more preferably about 1 to 50 µm. If the particle diameter of the particles does not fall below the lower limit of the above range, the light diffusing effect is insufficient. On the contrary, if the radius is outside the upper limit of the above range, coating of the resin composition forming the light diffusing layer 3 becomes difficult and after lamination. Undesirable results such as dropping of particles occur.

In addition, since the support 4 of the direct type backlight capable of obtaining a clear optical image according to the present invention needs to transmit light emitted from a light source, it is basically formed of a synthetic resin having excellent light transmittance. The synthetic resin used for the base sheet 2 is not particularly limited, and examples thereof include polyethylene telephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, acrylic copolymer, and polyester system. The copolymer, polystyrene copolymer, etc. can be mentioned. Moreover, in addition to the said polymer, additives, such as a plasticizer, a stabilizer, a deterioration inhibitor, a dispersing agent, an antifoamer, and a foaming agent, may be mix | blended with resin. The support not only serves as a support such as a diffusion film and a prism film formed on the support, but also maintains a constant distance from the lamp 6 to reduce the heat transferred from the lamp 6, the distance away from the lamp According to the role of increasing the function of the diffusion film to diffuse the form of light source emitted in a linear or point shape. The thickness of the support is preferably 0.5mm to 3mm, more preferably 1mm to 2mm. If the thickness is lower than the lower limit, it cannot maintain a flat shape and thus cannot serve as a support. If the upper limit is exceeded, the optical loss is increased to reduce the luminance and to increase the thickness of the display.

The support 4 may be added with a diffusion agent to impart a diffusion function. Particles to be used as the diffusing agent is not only organic particles such as acrylic resin, polyurethane, polyvinyl chloride, polystyrene, acrylic copolymer, polystyrene copolymer, polyacrylonitrile, polyamide, polymethyl methacrylate, but also silica, titanium Inorganic particles such as dioxide and calcium carbonate may also be used.

The adhesive layer 5 according to the present invention serves to bond the diffusion film 1 and the support 4 to a resin having a glass transition temperature lower than room temperature (25 ° C.). When the glass transition temperature is high, a problem may occur in that air is mixed due to unbonding in the process of laminating the diffusion film 1 and the support 4. Such adhesives include urea resins, melamine resins, phenol resins, epoxy resins, unsaturated polyester resins, alkyd resins, urethane resins, acrylic resins, polyurethanes, fluorine resins, silicone resins, and the like. A crosslinking agent, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersing agent, an antifoamer, a foaming agent, an antistatic agent, etc. may be mix | blended with the said resin.

The resin of the adhesive should be transparent and colorless so that it passes a lot of light and does not absorb a particular wavelength of visible light. In addition, the refractive index is preferably 1.43 to 1.59 in order to minimize reflection or optical loss in the portion of the support 4 and the diffusion film 1 forming the interface with the adhesive. This is because when the refractive index is higher than or equal to the upper limit, the reflection of light entering the adhesive layer from the support increases. When the refractive index falls below the lower limit, the reflection of light entering the diffusion layer from the adhesive layer increases, which causes a decrease in luminance.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example.

EXAMPLE

First, as the base sheet of the diffusion film, a biaxially stretched high-transparent polyester film (Toray Industries, Inc. XG533) was used. The diffusion layer of the diffusion film is coated on one surface of the polyester film (Toray Saen Co., Ltd. XG533-100um) according to the composition and process conditions of the following [Table 1], and then dried at 110 ° C. for 60 seconds to have a thickness of 30 μm. A phosphorus primary light diffusion film was prepared.

TABLE 1

Process conditions Total amount of composition 100 g Suzy Aekyung Chemical A-811 30 g particle SOKEN MX1000 30 g menstruum MEK 40 g

As the support, an acrylic resin having a thickness of 2 mm, in which an organic diffusion agent was included and given a diffusion function, was used. Using the conditions shown in Table 2, the adhesive was wet applied to the diffusion film, dried at 120 ° C. for 1 minute, and bonded to the support by a roll lamination method to prepare a direct backlight.

TABLE 2

Condition Adhesive refractive index Base film thickness (㎛) Example 1.49 50 Comparative Example 1 1.49 188 Comparative Example 2 1.42 50 Comparative Example 3 No adhesive 188 Comparative Example 4 No adhesive 100

[Comparative Example]

Comparative Examples 1 to 4 were prepared in the same manner as in Example. However, the conditions shown in Table 2 were used differently for each comparative example.

In Table 3, the brightness and the blurring of the Examples and Comparative Examples were measured.

TABLE 3

result Luminance (cd / m ² ) Phenomena Example 5240 ○ Comparative Example 1 5197 ○ Comparative Example 2 5192 ○ Comparative Example 3 5178 △ Comparative Example 4 5182 X

As can be seen in Table 3 according to the embodiment according to the present invention it can be seen that the luminance is much higher than the other comparative examples and hardly appearing phenomenon.

Hereinafter, a method of measuring and evaluating the luminance and murmur shown in Table 3 will be described.

Luminance measurement

The brightness was measured using a direct backlight unit to obtain a 32 "clear optical image. The diffuser sheet was cut and mounted on a light diffusion plate. The 25-point position was measured from the front (90 °) with the distance between -7 and the backlight unit as 25cm, and the average value was shown.

Wither measurement

Samples were assembled in a direct backlight to obtain a 32 "clear optical image, and the lamp was turned on for 250 hours and then decomposed to visually observe the degree of diffusion of the film and classified into ○, △, and X.

○: no change (keep flat)

△: partially excited state

X: The whole state is excited

In the present specification, only a few examples of various manufacturing and analysis experiments performed by the present inventors are described, but the technical idea of the present invention is not limited thereto, and may be variously modified and implemented by those skilled in the art. .

As described above, according to the direct type backlight capable of obtaining a clear optical image according to the present invention, it is possible to implement a backlight having no brightness unevenness by improving the moving phenomenon of the diffusion film and being lost by the air layer between the support and the diffusion film. By minimizing light, the brightness of the light may be improved, and the thickness of the base film may be reduced.

Therefore, according to the direct type backlight which can obtain a clear optical image according to the present invention, the brightness of the diffused film used in the direct type backlight which can obtain a clear optical image of a large-area LCD display is excellent in brightness and does not have a phenomenon. It can have an effect that can be used as an excellent material to increase the light efficiency.

Claims (3)

In the direct type backlight which can obtain a clear optical image, The direct type | mold which can obtain a clear optical image characterized by including the adhesive layer 5 adhere | attached between the support body 4 and the light-diffusion film 1 in which the light-diffusion layer 3 was formed in the base material sheet 2. Backlight. The direct type backlight of claim 1, wherein the refractive index of the adhesive layer (5) is 1.43 to 1.59. The method according to claim 1 or 2, A direct backlight capable of obtaining a clear optical image, wherein a thickness of the base sheet (2) used in the direct backlight is 10 µm to 150 µm.

Images