KR102447323B1 - Composition for optical film, optical film and backlight unit comprising the same - Google Patents

Abstract

The present invention relates to a composition for an optical film, an optical film, and a backlight unit including the same.
The composition for an optical film according to the present invention contains two types of polycarbonate resins having different molecular weights in a specific weight ratio, thereby lowering the coefficient of thermal expansion of a film obtained by molding the same and improving tear properties.
In addition, by replacing the commonly used polyethylene terephthalate resin, the stretching process or the primer treatment process can be omitted, thereby lowering the manufacturing cost and having optical properties equal to or higher than that of the polyethylene terephthalate resin. Luminance efficiency can be realized.

Description

A composition for an optical film, an optical film, and a backlight unit comprising the same

The present invention relates to a composition for an optical film, an optical film, and a backlight unit including the same, and more particularly, to an optical film containing a polycarbonate resin and having a low coefficient of thermal expansion, and a backlight unit including the same.

A display device is a device that visually displays data, and includes a liquid crystal display, an electrophoretic display, an organic light emitting display, and an inorganic EL display. , a Field Emission Display, a Surface-conduction Electron-emitter Display, a Plasma Display, and a Cathode Ray Display.

Among them, in particular, a liquid crystal display (LCD) has been in the spotlight in recent years due to the advantages of mass production technology, ease of driving means, realization of high image quality, and realization of a large-area screen.

A liquid crystal display device (LCD) is an electronic device that converts various types of electrical information generated in various devices into visual information by using a change in liquid crystal transmittance according to an applied voltage.

The liquid crystal display device can realize low power driving, a thin structure, and excellent image quality, and thus is widely used as an alternative means to overcome the disadvantages of the conventionally used cathode ray tube (CRT).

Such a liquid crystal display device consists of a liquid crystal panel bonded together with a liquid crystal layer interposed between two parallel substrates as an essential component, and an electric field is applied to the liquid crystal panel to change the arrangement direction of liquid crystal molecules to change the transmittance difference to implement

However, since the liquid crystal panel does not have a self-luminous element, a separate light source is required to display the difference in transmittance as an image.

The 　 backlight unit can be divided into a direct type and an edge type according to the location of the light source.

The direct type 　 backlight unit is a method of directly supplying the light emitted from the light source to the liquid crystal panel by arranging the light source under the liquid crystal panel.

The edge-type backlight unit is a method of indirectly supplying light emitted from the light source to the liquid crystal panel using refraction and reflection from the light guide plate by placing a light guide plate under the liquid crystal panel and arranging the light source on at least one side of the light guide plate. .

The backlight unit includes a plurality of optical sheets including at least one diffusion sheet and a prism sheet in order to improve the luminance of light emitted from the light source.

Each of these plurality of optical sheets forms an optical unit for condensing or diffusion on top of the supporting layer, which is an essential base material.

As the support layer, a polyethylene terephthalate (PET) substrate is most often used, and the PET substrate occupies a considerable cost in the optical sheet.

In addition, as such a plurality of optical sheets are provided, friction is generated between the sheets and scratches are generated, light cannot be emitted in a desired direction due to mutual interference, and the display quality is deteriorated as the luminance of the entire screen becomes non-uniform. There is this.

Among these problems, in order to prevent friction between the sheets, the thickness of each optical sheet can be thickened to prevent each optical sheet from flowing. , furthermore, there is a problem in that the manufacturing cost of the entire liquid crystal display device is increased.

Therefore, there is an attempt to simplify the process by not going through the stretching process, and to use a polycarbonate (PC) substrate that is moldable while having excellent impact resistance and heat resistance, but due to the nature of the polycarbonate resin, the amount of thermal expansion is high, so wrinkle defects occur There is a problem in that it is difficult to apply to a display device.

The present invention has been devised to solve the above-described problems, and the present invention provides a composition for an optical film in which a high molecular weight polycarbonate resin and a low molecular weight polycarbonate resin are mixed in a specific ratio, thereby providing an optical having a low coefficient of thermal expansion. It aims to provide a film.

In addition, an object of the present invention is to provide an optical film having less occurrence of wrinkles or tearing when applied to a backlight unit by providing the composition for an optical film.

Additionally, the optical film of the present invention aims to provide an optical film with reduced manufacturing cost by going through a simplified manufacturing process compared to the conventional polyethylene terephthalate film.

Another object of the present invention is to provide an optical film having a high transparency and a dense structure through the composition, thereby providing a reliable backlight unit that maintains luminance and image quality while reducing costs.

According to one aspect of the present invention for achieving the above object, it is possible to provide an optical film by melt extrusion molding a composition in which a high molecular weight polycarbonate resin and a low molecular weight polycarbonate are mixed in a specific ratio.

Specifically, the first polycarbonate resin and the second polycarbonate resin are included in a weight ratio of 95: 5 to 85: 15, and the weight average molecular weight of the first polycarbonate resin is greater than the weight average molecular weight of the second polycarbonate resin. A composition for a large optical film can be provided.

The first polycarbonate resin may be a high molecular weight polycarbonate resin, and may have a weight average molecular weight of 30,000 to 34,000.

The second polycarbonate resin may be a low molecular weight polycarbonate resin and may have a weight average molecular weight of 16,000 to 18,000.

As such, by including the relatively low molecular weight second polycarbonate resin in the ratio of the high molecular weight first polycarbonate resin and the above range, the low molecular weight polycarbonate resin is formed in the high molecular weight polycarbonate resin network space, that is, in the intermolecular voids. It can be added to reduce the air content between the molecules to improve the coefficient of thermal expansion.

The glass transition temperature of the composition may be 140 to 180 ℃.

In addition, the composition may further include an additive which is at least one of an inorganic filler, a heat stabilizer, a plasticizer, and a lubricant.

According to another aspect of the present invention, the first polycarbonate resin and the second polycarbonate resin are included in a weight ratio of 95: 5 to 85: 15, and the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, and the The weight average molecular weight of the second polycarbonate resin may provide an optical film obtained by molding a composition for an optical film of 16,000 to 18,000.

Specifically, as described above, by including two types of polycarbonate resins having different molecular weights in a mixing ratio optimized for the purpose of the optical film, the stretching step is omitted to provide an economical film with excellent transparency, thermal stability and chemical resistance can do.

The thickness of the film may be 50 to 200㎛.

The tear strength (tear 　 resistance) measured according to ASTM D 1004 standard of the film may be 150 g/cm to 200 g/cm.

The coefficient of thermal expansion (CTE) of the film may be 70 e ^-06 /℃ to 80 e ^-06 /℃.

A prism pattern may be provided on one surface of the optical film.

According to another aspect of the present invention, a light source unit, a light guide plate on the light source unit, and a prism sheet on the light guide plate, wherein the prism sheet is 95: 5 to 85: 15 of the first polycarbonate resin and the second polycarbonate resin of, the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, and the weight average molecular weight of the second polycarbonate resin is 16,000 to 18,000 An optical film obtained by molding a composition for an optical film comprising A backlight unit may be provided.

According to the present invention, by reducing the voids between molecules of the polycarbonate resin, it is possible to provide an optical film having a low coefficient of thermal expansion while having the advantages of impact resistance and heat resistance of the polycarbonate resin.

In addition, according to the present invention, by increasing intermolecular bonding energy and increasing elasticity, it is possible to provide an optical film having improved tear strength.

In addition, according to the present invention, there is no need for a stretching process or a primer treatment, so the manufacturing process can be simplified and the manufacturing cost can be lowered.

In addition, according to the present invention, since the above-described optical film is provided with a prism pattern on one surface thereof, when applied to a backlight unit, price competitiveness is high, and luminance efficiency and heat resistance are excellent.

1 is a schematic cross-sectional view of a prism sheet including an optical film according to an embodiment of the present invention.
2 is a cross-sectional view of a backlight unit according to an embodiment of the present invention.
3 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment.

Advantages and features of the present invention and methods for achieving them will become apparent with reference to the following embodiments. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, the present invention will be described in detail.

Composition for optical film

According to one aspect of the present invention, it is possible to provide a composition in which a high molecular weight polycarbonate resin and a low molecular weight polycarbonate are mixed in a specific ratio.

Specifically, the first polycarbonate resin and the second polycarbonate resin are included in a weight ratio of 95: 5 to 85: 15, and the weight average molecular weight of the first polycarbonate resin is greater than the weight average molecular weight of the second polycarbonate resin A composition for an optical film can be provided.

As used herein, "molecular weight (MW)" is a standard polymethyl methacrylate conversion value obtained by gel permeation chromatography (GPC) measurement using hexafluoro isopropanol as a solvent.

The polycarbonate resin used herein may be an aromatic polycarbonate resin or an aliphatic polycarbonate resin, and the type of polyester having a carbonate bond is not particularly limited.

The polycarbonate resin may be prepared by reacting a diphenol compound with a phosgene compound, a halogen acid ester compound, a carbonic acid ester, or a combination thereof.

As non-limiting examples of the diphenol compound, hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)propane ('bisphenol-A'), 2, 4-bis(4-hydroxyphenyl)-2-methylbutane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(3-chloro -4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro-4-hydroxyphenyl) propane, 2 ,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfoxide, bis(4-hydroxyphenyl)ketone, bis(4-hydroxyphenyl) Ether etc. are mentioned.

Of the above diphenols, preferably 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane or 1,1-bis(4-hydroxyphenyl)propane Hydroxyphenyl) cyclohexane can be used, and 2,2-bis (4-hydroxyphenyl) propane can be used more preferably.

Also, the polycarbonate resin may be a linear polycarbonate resin or a branched polycarbonate resin.

A specific example of the linear polycarbonate resin may be a bisphenol-A-based polycarbonate resin. A specific example of the branched polycarbonate resin may be a polymer prepared by reacting a polyfunctional aromatic compound such as trimelatic anhydride and trimellitic acid with diphenols and carbonate.

Specifically, the first polycarbonate resin may be represented by the following Chemical Formula 1, and n may be an integer of 220 to 250.

[Formula 1]

The second polycarbonate resin may be represented by Formula 1, and n may be an integer of 120 to 150.

In addition, the first polycarbonate resin may be a copolymer including a repeating unit represented by the following Chemical Formula 2, and m may be 10 to 50.

[Formula 2]

The second polycarbonate resin may be a copolymer including the repeating unit represented by Formula 2, and m may be 5 to 20.

Here, R1 to R8 are each independently hydrogen, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2- It may be selected from a C6 alkoxy group and a substituted or unsubstituted C1-C6 haloalkyl group.

As used herein, Ca-Cb alkyl is a saturated aliphatic group having a to b carbon atoms, including a straight chain alkyl group, a branched alkyl group, a cycloalkyl (alicyclic) group, an alkyl substituted cycloalkyl group, and a cycloalkyl substituted alkyl group. means a radical of

A straight chain or branched alkyl group has 10 or less (eg C1-C10 straight chain, C3-C10 comminuted), preferably 4 or less, more preferably 3 or less carbon atoms in its backbone.

Specifically, the alkyl group is methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pent-1-yl, pent-2-yl, pent-3-yl , 3-methylbut-1-yl, 3-methylbut-2-yl, 2-methylbut-2-yl, 2,2,2-trimethyleth-1-yl, n-hexyl, n-heptyl and n - May be octyl.

Likewise, preferred cycloalkyls have 3-10 carbon atoms in their ring structure, preferably 3,4,5,6 or 7 carbon atoms.

Specifically, a cycloalkyl group is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, cycloheptyl, bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, decalinyl or adamantylyl. can

In addition, haloalkyl means an alkyl substituted with fluoro (-F), chloro (-Cl), bromo (-Br) or iodo (-I). Such alkyls may contain one or more non-hydrogen substituents provided that attachment does not violate valence electron requirements.

For example, haloalkyl refers to -CH2(halo), -CH(halo)2 or -C(halo)3, and refers to a methyl group in which at least one of the hydrogens of the methyl group is replaced by a halogen, specifically, triple romethyl, trichloromethyl, tribromomethyl and triiodomethyl, and the like.

In addition, the polycarbonate resin may be a low-flow polycarbonate resin having a low melt index (MI), and specifically, according to ASTM D1238, the melt index (MI) is 10 g/10 min at a temperature of 200° C. and a load of 1.2 kg. to 30 g/10 min.

If the melt index is less than the above range, the film formability may be reduced, and if the melt index exceeds the above range, there is a risk that the impact resistance, chemical resistance, etc. of the film may be deteriorated.

In general, since polycarbonate resin has a relatively large molecular structure, there are many intermolecular voids, and the air in these voids expands and tends to have a high coefficient of thermal expansion.

When the coefficient of thermal expansion is high, when applied to a display device that generates heat, wrinkles tend to occur due to the interference between the film and the mechanical part, so that it is difficult to use as a base film such as a prism sheet of a backlight unit.

Accordingly, the present invention, as described above, by including two types of polycarbonate resins having different molecular weights in the above range, improved the above problems by controlling intermolecular voids and binding energy.

Specifically, the weight average molecular weight of the first polycarbonate resin included in the composition in a weight ratio of 95: 5 to 85: 15 may be 30,000 to 34,000, and the weight average molecular weight of the second polycarbonate resin is 16,000 to 18,000 can be

If only the first polycarbonate resin having a relatively high molecular weight is used, since the voids between molecules are large, when the air in the voids is expanded by heat, the intermolecular bonding energy does not suppress the expansion, so the film itself expands and the film hanger part It can be torn from the side.

At this time, by including the relatively low molecular weight second polycarbonate resin in a ratio within the above range, the low molecular weight polycarbonate resin is added to the high molecular weight polycarbonate resin network space to reduce intermolecular voids.

In addition, since the second polycarbonate resin having a low molecular weight can move when external stress is applied, the elasticity of the entire film is increased, and there is an advantage that it is not easily torn.

In addition, when the first polycarbonate resin is included in excess of the above range, the effect of adding the low molecular weight second polycarbonate resin is insignificant, so that the coefficient of thermal expansion may not be improved, and the second polycarbonate resin exceeds the above range. When it is included, there is a problem in that the mechanical strength of the entire film is weakened and chemical resistance is lowered.

Accordingly, by providing a composition including a polycarbonate resin having a high molecular weight and a polycarbonate resin having a low molecular weight within the above range, the physical properties of a film obtained by molding the same can be improved.

The glass transition temperature of the composition may be 140 to 180 ℃.

Since the composition for an optical film according to the present invention has a glass transition temperature (TG) of 140° C. or higher, it has high heat resistance and excellent moldability at high temperatures.

In addition, the composition may further include an additive which is at least one of an inorganic filler, a heat stabilizer, a plasticizer, and a lubricant.

Examples of the inorganic filler include, but are not limited to, talc, clay, mica, calcium silicate, glass, glass hollow sphere, glass fiber, calcium carbonate, magnesium carbonate, basic magnesium carbonate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc borate, dosonite. , ammonium polyphosphate, calcium aluminate, hydrotalcite, silica, diatomaceous earth, alumina, titanium oxide, iron oxide, zinc oxide, magnesium oxide, tin oxide, antimony oxide, barium ferrite, strontium ferrite, carbon black, graphite, carbon fiber, Activated carbon, carbon hollow spheres, calcium titanate, lead zirconate titanate, silicon carbide, and the like may be used.

In addition, the present invention may include a thermal stabilizer, specifically, the thermal stabilizer serves to prevent the thermoplastic resin from decomposing and aging under the influence of oxygen, light, or thermal energy in the atmosphere, thereby preventing deterioration of its original properties. will do

Specifically, with respect to 100 parts by weight of the composition for an optical film, the heat stabilizer may include 0.1 parts by weight to 5 parts by weight, preferably 2 parts by weight to 3 parts by weight. When the above ranges are satisfied, excellent effects of viscosity stability and thermal stability of the composition can be realized.

The thermal stabilizer is a Cd/Ba/Zn-based, Cd/Ba-based, Ba/Zn-based, Ca/Zn-based, Na/Zn-based, Sn-based, Pb-based, Cd-based, Zn-based organic composite powder stabilizer and combinations thereof. It may include at least one selected from the group consisting of, but is not limited thereto.

Preferably, it is preferable to use a Ba/Zn-based stabilizer as the thermal stabilizer, because the Ba/Zn-based stabilizer has good transparency and thermal stability and is suitable for a soft film.

The plasticizer included in the composition may be, for example, a benzoate-based plasticizer, a citrate-based plasticizer, or a phosphate-based plasticizer, and eco-friendliness may be achieved by using the plasticizer.

By adding a plasticizer, the bleeding phenomenon is further suppressed and, at the same time, compatibility with other components is maintained at an excellent level, so that desired physical properties can be easily realized.

The type of lubricant is not particularly limited, but it can promote eco-friendliness by including eco-friendly higher fatty acids, and specifically, stearic acid, which is a saturated higher fatty acid having 18 carbon atoms, can be used.

In addition, the lubricant may be included in an amount of about 3 parts by weight or less with respect to 100 parts by weight of the composition for an optical film, and thus effectively prevent the resin from adhering to the roll or press during processing such as pressing to form the transparent film. can be prevented

The composition for the optical film may further include other additives and the like, and the other additives may use various types of materials known in the art, and are not particularly limited.

optical film

According to another aspect of the present invention, the first polycarbonate resin and the second polycarbonate resin are included in a weight ratio of 95: 5 to 85: 15, and the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, and the The weight average molecular weight of the second polycarbonate resin may provide an optical film obtained by molding a composition for an optical film of 16,000 to 18,000.

The optical film may be obtained by melt extrusion molding the above-described composition for an optical film according to a method well known in the art.

In this case, the optical film may be obtained through a step of mixing and dissolving the first polycarbonate resin and the second polycarbonate resin by heating, an extrusion molding step, and a heat setting step, and the stretching step may be excluded.

The composition for an optical film according to the present invention contains two types of polycarbonate resins in a mixing ratio optimized for the purpose of the optical film, thereby omitting the stretching step and having excellent transparency, thermal stability and chemical resistance, so There is an economic advantage because the manufacturing cost can be omitted.

Specifically, the heating dissolution step may be performed by stirring in a solvent at a temperature at which the polycarbonate resin is completely dissolved, or by uniformly mixing in an extruder.

Preferably, the first polycarbonate resin is first melted, and then the second polycarbonate resin is post-added and melt-mixed.

The solvent is not particularly limited as long as it can sufficiently dissolve the polycarbonate resin, and examples thereof include aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, and liquid paraffin, but the solvent content is stable. In order to obtain a composition in a gel-like state, a non-volatile solvent such as liquid paraffin is preferred.

When dissolving in an extruder, first, the first polycarbonate resin is supplied and melted in the extruder. Thereafter, the second polycarbonate resin and the liquid solvent are supplied to the first polycarbonate resin in the molten state.

Subsequently, in the extrusion step, the heated solution of the melt-kneaded polycarbonate resin may be extruded from a die or the like directly or using a separate extruder so that the film thickness of the final product is 50 to 200 μm.

The solution extruded from the die is formed into a gel-like molding by cooling. Cooling is by cooling the die or cooling the gel sheet. Cooling is carried out at a rate of at least 50°C/min to 90°C or lower, preferably from 80 to 30°C. As a cooling method of the gel sheet, a method of direct contact with cold air, cooling water, or other cooling medium, a method of contacting a cooling roll, or the like can be used.

Then, the heat-set molding can be washed with a solvent to remove the remaining solvent. The cleaning solvent includes hydrocarbons such as pentane, hexane, and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as trifluoroethane, and ethers such as diethyl ether and dioxane. it is possible to use

These solvents are appropriately selected corresponding to the solvent used for dissolving the composition for an optical film and used alone or in combination. The washing method may be performed by a method of extraction by immersion in a solvent, a method of spraying a solvent, a method of combining these, and the like.

Subsequently, through the heat setting step, the gel-like molding may be heat set at a temperature of 125 to 135° C. for 15 seconds to 10 minutes. By heat setting at the time and temperature in the above range, there is an effect of reducing shrinkage due to heat setting and removing residual stress due to heat.

The thickness of the optical film obtained by molding in this way may be 50 to 200㎛.

If the thickness is less than 50㎛, cracks or curls may occur because it is difficult to implement a prism pattern on one side of the film or apply to a backlight unit to support the optical member, etc., and if the thickness exceeds 200㎛, the manufacturing cost will increase In addition, since the overall thickness of the backlight unit or display device including the same increases, there is a problem in hindering the implementation of a lightweight and thin display.

The tear strength (tear 　 resistance) measured according to ASTM D 1004 standard of the film may be 150 g/cm to 200 g/cm.

In addition, the coefficient of thermal expansion (CTE) of the film may be 70 e ^-06 / ℃ to 80 e ^-06 / ℃.

The optical film according to the present invention has a low coefficient of thermal expansion by mixing a high molecular weight polycarbonate resin with a low molecular weight polycarbonate resin in a specific ratio, filling intermolecular voids and remarkably reducing the amount of air expansion.

In addition, since the intermolecular bonding energy is increased and elasticity is increased by the fluidity of the low molecular weight polycarbonate resin, dimensional stability and tear strength are excellent, so that wrinkles or tearing when applied to a backlight unit can be significantly reduced.

In addition, a prism pattern 20 may be provided on one surface of the optical film.

The prism pattern may be formed by repeatedly arranging a plurality of first and second inclined surfaces symmetrical to each other to form a triangular cross-section and to be repeatedly arranged adjacently in the first direction (see FIG. 1 ).

The plurality of prism patterns 20 may be made of elastic acrylic, but the plurality of prism patterns 20 is not limited thereto.

On the other hand, although the optical film 10 as an embodiment of the present invention is used as a base layer and a prism pattern 20, which is one of the light collecting patterns, is illustrated and described as a light collecting layer for condensing light, but is not limited thereto, and the prism pattern 20 Instead, another shape, for example, a light collecting pattern such as a lenticular pattern having a semicircular or semi-elliptical cross-section may be formed.

As such, by including the prism pattern 20 on the optical film 10 according to the present invention, a film having a low coefficient of thermal expansion and high tearing strength is used as a base layer to improve the reliability of the prism sheet, and at the same time, the sheet It can reduce its own manufacturing cost.

backlight unit

According to another aspect of the present invention, the first polycarbonate resin and the second polycarbonate resin are included in a weight ratio of 95: 5 to 85: 15, and the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, The second polycarbonate resin may have a weight average molecular weight of 16,000 to 18,000 to provide a backlight unit including an optical film obtained by molding a composition for an optical film.

2 is a cross-sectional view of a backlight unit according to an embodiment of the present invention.

Referring to FIG. 2 , the backlight unit 200 may be divided into an edge type and a direct type according to a method in which the fluorescent lamp is positioned.

The edge type backlight unit 200 of FIG. 2 includes a reflective sheet 1 , a light guide plate 2 , a lamp 4 , a diffusion sheet 5 , a prism sheet 100 , and a protection sheet 6 .

The light source unit for generating light includes one or more lamps 4 and a mounting unit 3 . The light source unit for emitting light may use a cold cathode fluorescent lamp, and may generate light using a light emitting diode instead of the lamp 4 .

The mounting unit 3 mounts the lamp 4 and reflects the light generated from the lamp 4 . The light guide plate 2 can evenly spread the light generated from the light source unit over the entire light guide plate 2 by controlling the reflection conditions of the upper and lower surfaces thereof. Also, the light guide plate 2 may propagate the diffused light toward the panel of the liquid crystal display.

The reflective sheet 1 may reflect the light irradiated in the opposite direction to the panel of the liquid crystal display device through the light guide plate 2 in the direction of the light guide plate 2 .

The diffusion sheet 5 may diffuse or focus light traveling from the light guide plate 2 according to an angle between the light traveling from the light guide plate 2 and a normal line of the light guide plate 2 .

The prism sheet 100 may condense some of the light diffused or condensed by the diffusion sheet 5 toward the protective sheet 6 , and may reflect the remaining light toward the light guide plate 2 using reflective liquid crystals.

The prism sheet 100 may include an optical film 100 obtained with the composition for an optical film according to the present invention and a prism pattern 20 thereon.

The prism sheet 100 is provided with the advantages of abrasion resistance, impact resistance and chemical resistance of polycarbonate resin by including a low molecular weight polycarbonate resin together with a high molecular weight polycarbonate resin, and has a low coefficient of thermal expansion, so wrinkles do not occur and elasticity is good It has the advantage of high tear strength.

The protective sheet 6 may diffuse the light condensed by the prism sheet 100 in order to widen the viewing angle of the liquid crystal display panel, and provide the diffused light to the liquid crystal display panel.

The direct type backlight unit (not shown) is different from the edge type backlight unit in the position of the lamp and the provision of the light guide plate.

In the direct type backlight unit, the lamp 4 is positioned between the diffusion sheet 5 and the reflective sheet 1 , so that light can be directly irradiated toward the panel without the light guide plate 2 .

liquid crystal display

3 is a cross-sectional view of a liquid crystal display 300 including a backlight unit 200 including an optical film according to the present invention.

Referring to FIG. 3 , the liquid crystal display 300 includes a liquid crystal display panel and a backlight unit 200 . The backlight unit 200 may be a direct type or edge type backlight unit.

The liquid crystal display panel includes a TFT substrate 51 provided with a gate line, a data line, a thin film transistor (TFT), a pixel electrode, and the like, and disposed opposite to the TFT substrate, and includes a color filter and a common electrode. It is composed of the provided color filter substrate 50 and the liquid crystal layer 60 filled with liquid crystal between the TFT substrate 51 and the color filter substrate 50 .

The TFT substrate 51 is a transparent glass substrate provided with a matrix thin film transistor, and a data line is connected to a source terminal and a gate line is connected to a gate terminal. A pixel electrode made of transparent indium tin oxide (ITO) as a conductive material is provided at the drain terminal.

A color filter substrate 50 is disposed thereon to face the TFT substrate 51 . The color filter substrate 50 is a substrate in which R, G, and B pixels, which are color pixels in which a predetermined color is expressed while light passes, are provided by a thin film process, and a common electrode made of ITO is provided on the entire surface.

The liquid crystal layer 60 is provided between the TFT substrate 51 and the color filter substrate 50, the liquid crystal is filled therein, and liquid crystal cells constituting a pixel unit are arranged in a matrix form. The liquid crystal cell has an image by adjusting the light transmittance by changing the arrangement according to the image signal information.

In addition, polarizing plates 40 and 41 for polarizing unpolarized light provided from a light source into linearly polarized light are provided on the lower portion of the TFT substrate 51 and the upper portion of the color filter substrate 50 . The polarizing plates 40 and 41 maintain a constant transmission direction of light according to the alignment direction of the liquid crystal cell of the liquid crystal layer 60 .

In addition, the backlight unit 200 is provided on the rear surface of the TFT substrate 51 to supply light to the liquid crystal display panel.

As a result, the light provided from the backlight unit 200 including the prism sheet provided with the prism pattern using the optical film according to the present invention as the base film may be incident on the color filter corresponding to the molecular arrangement of the liquid crystal layer 60 . have.

In the above, although the embodiment of the present invention has been mainly described, various changes or modifications may be made at the level of those skilled in the art. Accordingly, it will be understood that such changes and modifications are included within the scope of the present invention without departing from the scope of the present invention.

300: liquid crystal display device
200: backlight unit
100: prism sheet
10: optical film
20: prism pattern
1: Reflective sheet
2: light guide plate
3: Implementation unit
4: lamp
5: diffusion sheet
6: Protection sheet
40, 41: polarizing film
50, 51: substrate
60: liquid crystal layer

Claims (12)

95:5 to 85:15 of a first polycarbonate resin including a plurality of first pores having a first size, and a second polycarbonate resin added in the first pores to decrease the first size of the first pores Included in the weight ratio of
The weight ratio of the first polycarbonate resin has a greater weight ratio than the weight ratio of the second polycarbonate resin in the composition,
When the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, the weight average molecular weight of the second polycarbonate resin is 16,000 to 18,000 smaller than the weight average molecular weight of the first polycarbonate resin,
A composition for an optical film.
delete delete According to claim 1,
The glass transition temperature of the composition is 140 to 180 ℃,
A composition for an optical film.
According to claim 1,
The composition further comprises an additive which is at least one of an inorganic filler, a heat stabilizer, a plasticizer, and a lubricant,
A composition for an optical film.
95:5 to 85:15 of a first polycarbonate resin including a plurality of first pores having a first size, and a second polycarbonate resin added in the first pores to decrease the first size of the first pores Included in the weight ratio of
The weight ratio of the first polycarbonate resin has a greater weight ratio than the weight ratio of the second polycarbonate resin in the composition,
When the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, the weight average molecular weight of the second polycarbonate resin is 16,000 to 18,000 smaller than the weight average molecular weight of the first polycarbonate resin. Molding the composition for an optical film obtained by
optical film.
7. The method of claim 6,
The thickness of the film is 50 to 200㎛,
optical film.
7. The method of claim 6,
The tear resistance measured according to ASTM D 1004 standard of the film is 150 g / cm to 200 g / cm,
optical film.
7. The method of claim 6,
The coefficient of thermal expansion of the film (Coefficient of Thermal Expansion, CTE) is 70 e ^-06 / ℃ to 80 e ^-06 / ℃,
optical film.
7. The method of claim 6,
A prism pattern is provided on one surface of the optical film,
optical film.
light source unit;
a light guide plate on the light source unit; and
and a prism sheet on the light guide plate.
The prism sheet,
95:5 to 85:15 of a first polycarbonate resin including a plurality of first pores having a first size, and a second polycarbonate resin added in the first pores to decrease the first size of the first pores But, the weight ratio of the first polycarbonate resin has a greater weight ratio than the weight ratio of the second polycarbonate resin in the composition,
When the weight average molecular weight of the first polycarbonate resin is 30,000 to 34,000, the weight average molecular weight of the second polycarbonate resin is 16,000 to 18,000 smaller than the weight average molecular weight of the first polycarbonate resin. Molding the composition for an optical film comprising the optical film obtained by
backlight unit.
According to claim 1,
The first polycarbonate resin or the second polycarbonate resin has a melt index (MI) of 10 g/10 min to 30 g/10 min under a temperature of 200 °C and a load of 1.2 kg.

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