KR101068438B1 - Multifunctional sheet for back light unit - Google Patents

Abstract

The present invention relates to a composite sheet for a backlight unit.

In the composite sheet for a backlight unit of the present invention, the material of the diffusion plate and the optical sheet is made of polycarbonate resin alone or blend resin of 50 to 95% by weight of polycarbonate resin and 5 to 50% by weight of copolyester resin, As the structure in which the diffusion plate and the optical sheet are integrated, foreign matters can be prevented from penetrating between the sheets, the scratch resistance due to the friction between the sheets can be improved, and the manufacturing process of the backlight unit is simplified. The cost can be reduced. Furthermore, thermal expansion and contraction heat resistance, hygroscopicity, and sheeting phenomenon can be improved by the same thermal behavior due to the use of the same material.

Backlight Unit, Polycarbonate, Copolyester, Diffusion Plate, Diffusion Sheet, Prism

Description

Composite sheet for backlight unit {MULTIFUNCTIONAL SHEET FOR BACK LIGHT UNIT}

The present invention relates to a composite sheet for a backlight unit, and more particularly, a diffusion plate and an optical sheet are formed of the same material consisting of polycarbonate resin alone or a blend resin of polycarbonate resin and copolyester resin. As the diffusion plate and the optical sheet are integrated, external foreign matter penetration is prevented between the sheets, and the thermal expansion and contraction heat resistance, hygroscopic resistance, and sheet phenomena are improved by the same thermal behavior due to improved scratch resistance and use of the same material. The improved composite sheet for a backlight unit.

The market for information display devices continues to expand due to the development and digitization of the information industry, and flat panel displays are replacing CRTs, which have been a major part of the existing information display devices.

In particular, the liquid crystal display (hereinafter referred to as 'LCD') technology has the advantage of being thinner with the development of mobile display technology and the enlargement of TV, and its low power consumption, so that the area of use among the flat panel display is mobile phone, car navigation, It is widely used from 1 inch to 50 inches such as display devices, monitors, and large TVs of various facilities and machinery.

LCD was first discovered at the end of the 19th century and it took some time before it was applied to the early display devices. However, the technology is rapidly being advanced and the price is being reduced as it is applied to the rudimentary display devices such as the electronic calculator and the electronic clock in the mid-20th century. .

In the TV sector, LCD systems are competing with slim CRT, plasma display (PDP) and projection displays, and the market size is expected to grow by 20% every year until 2010, with the sharpness, response speed, and color reproducibility of the displays greatly improved. It is expected.

The LCD device is largely composed of an LCD panel unit and a backlight unit (hereinafter referred to as 'BLU'), and the LCD panel does not have a structure capable of emitting light by itself and merely has a function of transmitting light on the rear side. Therefore, an LCD device cannot display an image at night or in a light-free space without the help of a back light, so a separate light source such as a BLU is required.

BLU is composed of lamp, sheet, mechanical part and driving circuit. Cold cathode fluorescent lamp (CCFL) and light emitting diode (LED) in BLU can produce uniform light across the entire area when using linear or point light source. Since it is not possible to provide a light guide plate or a diffuser plate, a reflecting plate, a prism sheet, a frame or the like, and the mechanism portion, the components are combined according to the characteristics of the BLU.

According to the recent technology trend, the performance of BLU parts seems to be nearing the optimum point, and the focus is on cost reduction, and the cost reduction through the improvement of yield or the change of composition has reached its limit. B. Cost reduction by changing manufacturing processes is a trend in the parts industry.

In particular, the development of technology for eliminating the diffusion sheet or prism sheet or developing the diffusion plate removal through the development of a surface light source through the development of a composite diffusion plate combined with a diffusion plate and a diffusion sheet, a diffusion plate and a prism sheet.

However, according to the related art, in the case of the BLU to which the surface light source is not applied, the diffusion plate, the diffusion sheet, and the prism sheet are simply loaded and used, and each sheet moves separately, causing scratches, uneven brightness or between the sheets. Foreign matter easily penetrates, causing a problem in the backlight unit.

In addition, the BLU temperature rises to 80 ° C. due to heat generated from the lamp and the inverter of the light source, causing thermal expansion of the optical sheet, which causes sheet shifting to degrade brightness uniformity on the LCD panel.

Accordingly, in order to solve the above problem, the diffusion plate and the optical sheet are designed to be larger or smaller than the required size, so that a tolerance occurs, which causes scratches due to friction between the sheets due to transportation or vibration of the product. It may cause the failure of the white spot in the attached state.

In general, the diffusion plate is designed to be 2.5 to 3.0mm smaller than the mold frame, and the diffusion sheet and the brightness enhancement sheet are fixed in consideration of the coefficient of thermal expansion during punching for fixing to the fixing pins of the mold frame to minimize movement in the mold frame. It is designed slightly larger than the pin.

Accordingly, the optical sheet can develop a material having improved scratch resistance to prevent friction scratches with the diffusion plate and the diffusion plate mold frame. However, since the optical sheet is different from the previously developed diffusion plate and prism sheet, the thermal behavior is different. This is not the same, which causes the problem of sheet warping.

In addition, a large area display requires a high light source, which requires high physical properties in the heat resistance of the diffuser plate, and on a small screen, the distance between the observer and the display is very short, so that small defects on the screen may be easily displayed. Therefore, high dimensional stability and reliability are required, and in this regard, since the diffusion plate undergoes more severe shape deformation at higher temperatures, it is also required to develop a general-purpose resin having excellent heat resistance and water resistance.

In general, the conventional diffusion plate is a polymethyl methacrylate (PMMA), polystyrene (PS), methyl styrene (MS), polycarbonate (PC) is the mainstream, the base of the diffusion sheet is biaxially stretched polyethylene terephthalate (PET) is used, and the prism sheet is also manufactured by coating polymethylmethacrylate (PMMA) on a polyethylene terephthalate (PET) material and forming a prism through drying and heat curing after molding the patterned mold.

Accordingly, the present inventors endeavored to solve the problems of the prior art, as a result of manufacturing a composite sheet in which a diffusion plate and an optical sheet made of polycarbonate resin alone or a blending resin of polycarbonate resin and copolyester resin are integrated. By confirming that the scratch resistance of the composite sheet due to the same material and the sheet hum is improved, the present invention was completed.

It is an object of the present invention to provide a composite sheet for a backlight unit in which a diffusion plate and an optical sheet are integrated.

It is another object of the present invention to provide a composite sheet for a backlight unit, in which a diffusion plate and an optical sheet are made of the same material, thereby improving reliability at high temperature and high humidity.

The present invention provides a composite sheet for a backlight unit in which a diffusion plate and an optical sheet are made of a polycarbonate resin alone or a blend resin of 50 to 95% by weight of a polycarbonate resin and 5 to 50% by weight of a copolyester resin. .

The copolyester resins include poly (1,4-cyclohexylenedimethylene terephthalate), poly (1,4-cyclohexylenedimethylene naphthalenedicarboxylate) and poly (1,4-cyclohexylene di Methylene 1,4-cyclohexanedicarboxylate).

At this time, the optical sheet is made of a diffusion sheet and a prism sheet, the diffusion sheet may be laminated one to three more.

The composite sheet may be interlayer bonded by a method selected from the group consisting of an adhesive between the diffusion plate and the optical sheet, double-sided tape, hot melt, high frequency, and thermal bonding, and may be integrated by ultrasonic thermal bonding of 10 to 25 kHz. have.

In the composite sheet for a backlight unit of the present invention, the diffusion plate and the optical sheet are integrated to prevent external foreign matter from penetrating into the inside, and scratch resistance due to inter-sheet friction can be improved. As it is simplified, the production cost is reduced.

In addition, in the composite sheet for a backlight unit of the present invention, the diffusion plate and the optical sheet are made of the same material of polycarbonate resin alone or blend resin composed of polycarbonate resin and copolyester resin, so that each sheet has the same thermal behavior. By matching the physical properties such as thermal expansion coefficient, shrinkage heat resistance and moisture absorption resistance can minimize the defect of the composite sheet due to the material difference, such as sheet thickness.

Hereinafter, the present invention will be described in more detail.

The present invention provides a composite sheet for a backlight unit in which a diffusion plate and an optical sheet are made of a polycarbonate resin alone or a blend resin of 50 to 95% by weight of a polycarbonate resin and 5 to 50% by weight of a copolyester resin. .

In the composite sheet for a backlight unit of the present invention, the diffusion plate and the optical sheet made of the same material are integrated, and the polycarbonate resin alone or the polycarbonate resin and the copolyester resin are mixed at an optimum ratio, thereby providing heat resistance and heat resistance. Absorption can be improved, and application to a composite sheet is advantageous compared to polyethylene terephthalate, polystyrene and acrylic resins conventionally used as optical sheets.

The blend resin is preferably a mixture of 50 to 95% by weight of polycarbonate resin and 5 to 50% by weight of copolyester-based resin, the heat resistance of the composite sheet is lowered if the content of the polycarbonate resin is less than 50% by weight A problem arises.

The polycarbonate resin is not particularly limited, but an aromatic polycarbonate is preferable, and more preferably, a polycarbonate resin containing bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] is applied. .

The copolyester-based resin preferably contains 1,4-cyclohexanedicarboxylic acid as a main component, and as an acid component, terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid alone or a mixture of two or more thereof Ethylene glycol and 1,4-cyclohexanedimethanol (CHDM) may be used as the glycol component, and more preferably, as a copolyester-based resin, poly (1,4-cyclohexylenedimethylene tere) Phthalate) (PCT), poly (1,4-cyclohexylenedimethylene naphthalenedicarboxylate) (PCN) and poly (1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) ( PCC) can be used.

More specifically, the blend resin may be 50 to 95% by weight of the polycarbonate resin and 5 to 50% by weight of the copolyester-based resin.

In this case, the acid component of the copolyester-based resin, selected from the group consisting of terephthalic acid, naphthalenedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid based on a total of 100 mol% of dicarboxylic acid It is composed of 80 to 100 mol% of acid component and 0 to 20 mol% of dicarboxylic acid containing 4 to 40 carbon atoms, and is a glycol component of copolyester-based resin, based on a total of 100 mol% of glycol units. When it is, 1 to 60 mol% of ethylene glycol, 40 to 99 mol% of 1,4-cyclohexanedimethanol and 0 to 20 mol% of glycol having 3 to 13 carbon atoms.

In addition, the acid component of the copolyester-based resin, composed of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and mixtures thereof based on a total of 100 mol% of dicarboxylic acid A glycol component of the copolyester-based resin consisting of 65 to 85 mol% of an acid component selected from the group consisting of 15 to 35 mol% of isophthalic acid and 0 to 20 mol% of a dicarboxylic acid containing 4 to 40 carbon atoms. For example, based on a total of 100 mol% of the glycol unit, it may be composed of 80 to 100 mol% of 1,4-cyclohexanedimethanol and 0 to 20 mol% of glycol having 3 to 13 carbon atoms.

In addition, the blend resin may further contain a thermal stabilizer 60 to 120ppm in consideration of the yellowing problem.

More specifically, the optical sheet made of a polycarbonate resin alone or a blend resin of a polycarbonate resin and a copolyester resin applied to the present invention has a light transmittance (TT) of less than 90% based on a thickness of 0.4 mm and less than 1.0%. It has a haze, glass transition temperature of 100-140 degreeC, and water absorption of 0.09-0.30 weight%.

The diffusion plate and the optical sheet of the polycarbonate resin alone or blend resin of the above is specifically, at least one selected from the group consisting of a diffusion sheet and a prism sheet is adhered on the diffusion plate, the diffusion sheet is one to three more Can be stacked.

In particular, a preferred embodiment of the present invention, as shown in Figure 1, the diffusion sheet 3, the prism sheet 4 and the diffusion sheet 3 made of the same material on the diffusion plate 1 is sequentially laminated The edges or periphery of each layer are bonded by the adhesive layer 2 to form an integrated structure.

The diffusion plate 1 is a polycarbonate resin alone, or a blend resin of polycarbonate resin and copolyester resin is coextruded, and UV stabilizer may be added to the surface layer to impart UV durability.

At this time, the thickness of the diffusion plate 1 is preferably 0.5mm to 2.0mm, if the thickness is 0.5mm or less can not support the optical sheet laminated on top, if the thickness is 2.0mm or more problem that the light loss is large have.

The diffusion sheet 3 and the prism sheet 4 are formed by co-extrusion of the same resin as the composition of the diffusion plate 1 and consist of a core layer and a surface layer. Thickness is preferred.

The adhesive layer 2 may be an adhesive, double-sided tape, hot melt, high frequency, thermal bonding, and ultrasonic waves as a means for integrating and integrating a diffusion plate, a diffusion sheet, and a prism sheet.

In this case, when the adhesive is applied, light is absorbed by the adhesive while the light passes through the adhesive layer, so that the amount of light transmission decreases and the luminance decreases. .

More preferably, ultrasonic waves of 10 to 25 kHz may be applied as the intersheet thermal bonding means.

Hereinafter, the manufacturing method of the composite sheet of the present invention will be described in detail.

The composite sheet of the present invention is a blend resin of (1) polycarbonate-based resin alone or polycarbonate-based resin 50 to 95% by weight and copolyester 5 to 50% by weight based on 1,4-cyclohexanedicarboxylic acid as a main component Coextruding the phosphorus composition to produce a 0.5 mm to 2.0 mm thick diffuser plate having a core layer and a surface layer formed thereon; (2) coextruding the polycarbonate resin alone or the blend resin to produce a 0.2 mm to 0.5 mm thick diffusion sheet having a core layer and a surface layer; (3) co-extruding the polycarbonate resin alone or the blend resin to prepare a prism sheet having a thickness of 0.2 mm to 0.5 mm having a core layer and a surface layer; And (4) sequentially integrating edges or peripheries of the diffusion plates, diffusion sheets, and prism sheets prepared in the above steps (1) to (3) by applying double-sided tape, hot melt, high frequency, thermal bonding, or ultrasonic waves; It can be prepared as.

At this time, the mixing ratio of the polycarbonate resin and copolyester-based resin and the applicable specific composition is the same as described above.

In the composite sheet manufacturing method of the present invention, the surface layer of the diffusion plate and the surface layer of the diffusion sheet may further contain 10 parts by weight of an antiblocking agent, slip agent and UV-resistant agent based on the polycarbonate resin alone or the entire blend resin. have.

In addition, the diffusion sheet may be coated with a mixture of polycarbonate-based binder resin and polymethyl methacrylate-based organic particles on the surface layer in order to improve light transmittance, wherein the material of the diffusion sheet and the binder resin is the same, It has the same thermal behavior and is excellent in optical reliability of the optical sheet due to thermal expansion, shrinkage heat resistance, hygroscopicity and the like even in an environment of high temperature and high humidity.

That is, in the composite sheet of the present invention, as the optical sheets are bonded to each other on the diffusion plate to form an integrated structure, the foreign sheet can prevent foreign substances from penetrating between the sheets, and scratches are caused by friction between sheets. The problem may be improved, and in particular, the scratches due to contact between the diffusion plate and the diffusion sheet, the diffusion sheet, and the prism sheet may be improved.

Particularly, in the composite sheet, the diffusion plate and the optical sheet are made of the same material of the polycarbonate resin alone or the blend resin of the polycarbonate resin and the copolyester resin, and thus have the same thermal behavior between the sheets. Also in the sheet expansion phenomenon due to thermal expansion, shrinkage heat resistance, hygroscopic resistance and the like can be improved.

Hereinafter, the present invention will be described in detail with reference to examples.

The following examples are merely illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

< Example  1>

One. Diffuser  Produce

The core layer is copolyester-based resin (poly 1,4-cyclohexylenedimethylene terephthalate) mainly composed of 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydride). Hydroxyphenyl) propane] was blended in a 4: 6 ratio and blended with a phosphite thermal stabilizer at 3.0 parts by weight based on the total content, and a silicone-based diffusing agent (Nikko-Rica, MSP- 0.5 part by weight of S020 product, 2 μm) was added.

The resin ratio of the surface layer is the same as that of the core layer, and 1.0 weight part of antiblocking agent (Montan wax), 2.0 weight part of slip agent (calcium carbonate particles), and UV-resistant agent (Shiba Inc., Tinuvin 234 Motel) 0.3 Part by weight was further added.

The resin of the core layer and the surface layer was coextruded to prepare a diffuser plate having a thickness of 1.5 mm.

2. Diffusion Sheet Manufacturing

The resin ratio of the core layer and the surface layer was the same as that of the diffusion plate to produce a substrate having a thickness of 200 μm. Dispersion by part was coated on a single layer to prepare a diffusion sheet.

3. Fabrication of Prism Sheet

The resin ratio between the core layer and the surface layer was the same as that of the diffusion plate, and a prism sheet having a thickness of 280 μm was prepared by passing the molten polymer through a roll engraved with a prism pattern during extrusion.

4. Fabrication of integrated composite sheet

After cutting the manufactured diffusion plate, diffusion sheet, prism sheet to 32 inches, and cut SK900 double-coated tape of Greentech to 5 mm width, the two sides on the four sides of the diffusion plate / diffusion sheet / prism sheet / diffusion sheet Tape was laminated sequentially to prepare an integrated composite sheet.

< Example  2>

An integrated composite sheet was prepared in the same manner as in Example 1 except that the copolyester-based resin and polycarbonate-based resin containing 1,4-cyclohexanedicarboxylic acid as a main component were mixed at a weight ratio of 3: 7. Was prepared.

< Example  3>

An integrated composite sheet was prepared in the same manner as in Example 1 except that the copolyester-based resin and polycarbonate-based resin containing 1,4-cyclohexanedicarboxylic acid as a main component were mixed at a weight ratio of 2: 8. Prepared.

< Example  4>

An integrated composite sheet was prepared in the same manner as in Example 1 except that the copolyester-based resin and polycarbonate-based resin containing 1,4-cyclohexanedicarboxylic acid as a main component were mixed at a weight ratio of 1: 9. Prepared.

< Example  5>

After loading the diffusion plate / diffusion sheet / prism sheet / diffusion sheet in order, except that the ultrasonic bonding of each layer by applying an ultrasonic wave of 10 to 25kHz to carry out in the same manner as in Example 1 to produce an integrated composite sheet It was.

< Comparative example  1>

After loading the diffusion plate / diffusion sheet / prism sheet / diffusion sheet in the order, the sheet was prepared in the same manner as in Example 1, except that it was performed without the integration process.

< Comparative example  2>

In the same manner as in Example 1, except that three diffusion sheets using an acrylic binder (model Shindo Intertek, SD743) were loaded on the polyester stretched film in mass production on the diffusion plate prepared in Example 1. A composite sheet was prepared by the execution.

< Comparative example  3>

On the diffusion plate manufactured in Example 1, a diffusion sheet using an acrylic binder in an existing polyester stretched film in mass production (model Shindo Intertek, SD743), a brightness-enhanced film BEF film (3M company) which is a prism sheet of polyethylene terephthalate series ) And DBEF film (3M), except that the stacking was carried out in the same manner as in Example 1 to prepare a composite sheet.

< Comparative example  4>

On the polystyrene-based diffusion plate (Dongwoo Fine Chem Co., Ltd., model RM803S), except that three sheets of diffusion sheet (Shinhwa Intertek Co., SD743 model) using an acrylic binder were loaded on a polyester stretched film in mass production. In the same manner as in Example 1 to prepare a composite sheet.

< Comparative example  5>

A composite sheet was manufactured in the same manner as in Comparative Example 2, except that a diffusion plate made of a composition in which a polystyrene resin and a polymethyl methacrylate resin were mixed at an 8: 2 weight ratio was applied.

< Comparative Example 6>

Diffusion sheet using an acrylic binder in a polyester stretched film in mass production on a diffusion plate made of a composition in which a polystyrene resin and a polymethyl methacrylate resin are mixed at an 8: 2 weight ratio (Shinhwa Intertek, SD743 Model), polyethylene A composite sheet was prepared in the same manner as in Example 1, except that the luminance-enhanced film BEF film (3M company) and DBEF film (3M company), which were terephthalate series prism sheets, were loaded in this order.

< Experimental Example >

The composite sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were evaluated for the following physical properties and the results are shown in Tables 1 and 2.

One. Scratch resistance  evaluation

After assembling the composite sheet prepared in Examples 1 to 5 and Comparative Examples 1 to 6 in the LTA460WT-L14, the vibration was changed to 0 to 300 Hz for 30 minutes in the X, Y, and Z directions, respectively, and then decomposed by scratching. Was evaluated visually.

As a result of measurement, if white light does not occur when the backlight is turned on, and if dust or scratch does not occur when the backlight is disassembled, it is very good (○), no white point occurs, dust does not occur, and a lot of scratches occur. (△), when a white point and dust were observed, it determined with defect (x).

2. Seat um evaluation

Assemble the back light unit with the manufactured composite sheet and leave it in a thermo-hygrostat for 72 hours at 60 ° C and 75 RH%, cool it at room temperature for 1 hour, turn on the backlight, and after 1 hour If the sheet is not visible from the front and side by visual evaluation, it is very good (○) .If the sheet is not seen from the front, but the sheet is visible when viewed from the side of 45 degrees, usually (△), When sheet thickness was confirmed from the front, it determined with defect (x).

3. Luminance Evaluation

The manufactured composite sheet was mounted on a backlight unit (Tasan LCD, LTA32OW2-L01), and Topcon BM-7 was mounted under the conditions of a cold cathode fluorescent lamp (CCFL) voltage of 16.5V and a dimming value of 2.8V. Luminance was measured on the stage.

4. Uniformity Assessment

Dividing the manufactured composite sheet into 6 parts by short axis and 6 parts by long axis to display the positions of 1/6, 3/6, 6/5, and measure the 9-point luminance at each location. The uniformity was evaluated by the ratio based on the following equation (1). According to Equation 1, uniformity corresponds to 95% when the luminance minimum value is 9800 and the luminance maximum value is 10,300.

Uniformity (%) = minimum luminance value / maximum luminance value × 100

division Example 1 Example 2 Example 3 Example 4 Example 5 Configuration BLU Configuration Diffuser Plate / Diffusion Sheet / Prism Sheet / Diffusion Sheet responsibility Scratch resistance ○ ○ ○ ○ ○ Situm Visual check ○ ○ ○ ○ ○ optics
characteristic BM-7 Luminance (nit) 10,633 10,685 10,729 10,784 10,635 Uniformity (%) 94 94 94 94 94

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Configuration BLU Configuration Diffuser Plate / Diffusion Sheet / Prism Sheet / Diffusion Sheet responsibility Scratch resistance △ ○ ○ ○ ○ ○ Situm Visual check ○ △ △ △ △ △ optics
characteristic BM-7 Luminance (nit) 10,624 10,250 7,540 10,432 10,414 7,854 Uniformity (%) 94 93 91 94 94 91

Examples 1 to 5 are composed of an optical sheet of the same material made of a blend resin of polycarbonate and polyester resin, and the use of the resin confirmed excellent scratch resistance and overall reliability even at high temperature and high humidity. , Comparative Examples 1 to 6, which are not integrated between sheets, and Comparative Examples 2 to 6, in which a diffusion sheet and a prism sheet stacked on a diffusion plate are manufactured by loading a material having a different composition, do not satisfy the reliability of sheet thickness.

In addition, the composite sheet of the present invention satisfies optical properties in terms of brightness and uniformity, thereby improving thermal expansion and contraction heat resistance, hygroscopicity, and sheet hum by the same thermal behavior due to the use of the same material. The optical sheet is integrated to simplify the manufacturing process of the backlight unit.

As a result of the above, the present invention can simplify the BLU assembly process as a composite sheet in which the diffusion plate and the optical sheet used in the backlight unit of the liquid crystal display are integrated, and between the diffusion plate and the diffusion sheet, the diffusion sheet and the diffusion sheet The foreign material can be prevented from penetrating, and the scratch resistance due to the inter-sheet friction can be improved.

In addition, since the diffusion plate and the optical sheet of the present invention is made of the same composition of polycarbonate-based resin alone or blend resin of polycarbonate-based resin and copolyester-based resin, each sheet has the same thermal behavior, resulting in thermal expansion coefficient and shrinkage heat resistance, As the moisture resistance is matched, physical properties due to material differences such as sheet thickness can be improved to minimize defects of the backlight unit.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications belong to the appended claims. .

1 is a cross-sectional view of a composite sheet for a backlight unit of the present invention.

<Code Description of Main Parts of Drawing>

1 : diffuser plate

2 : adhesive layer

3 : diffusion sheet

4 : Prism Sheet

Claims (6)

Polycarbonate resin alone or Diffusion plate and optical sheet consisting of a blend resin of 50 to 95% by weight of polycarbonate resin and 5 to 50% by weight of copolyester resin, The diffusion sheet and the optical sheet is a composite sheet for a backlight unit, characterized in that the interlayer adhesion by ultrasonic bonding. The method of claim 1, wherein the copolyester-based resin is poly (1,4-cyclohexylenedimethylene terephthalate), poly (1,4-cyclohexylenedimethylene naphthalene dicarboxylate) and poly (1, 4-cyclohexylene dimethylene 1,4-cyclohexanedicarboxylate) composite sheet for the backlight unit selected from the group consisting of. The composite sheet for a backlight unit according to claim 1, wherein the optical sheet includes a diffusion sheet and a prism sheet, wherein one to three sheets of the diffusion sheet are stacked. delete delete The composite sheet for a backlight unit of claim 1, wherein the ultrasonic wave ranges from 10 to 25 kHz.

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