WO2007043847A1

WO2007043847A1 - Antistatic light diffusion film

Info

Publication number: WO2007043847A1
Application number: PCT/KR2006/004157
Authority: WO
Inventors: Kwang Suck Suh
Original assignee: Kwang Suck Suh
Priority date: 2005-10-13
Filing date: 2006-10-13
Publication date: 2007-04-19
Also published as: KR20070087750A; KR100886027B1

Abstract

Disclosed herein is an antistatically treated light diffusion film for liquid crystal display devices. The light diffusion film has antistatic performance to prevent foreign matter from adhering thereto and static electricity from being generated thereon and, at the same time, has improved optical properties such as haze and total light transmittance.

Description

ANTISTATIC LIGHT DIFFUSION FILM

Technical Field

[1] The present invention relates to a light diffusion film or sheet (hereinafter, referred to as "film") for liquid crystal display devices, which comprises a transparent plastic film as a substrate, and, more particularly, to a transparent plastic film-based light diffusion film for liquid crystal display devices, which transmits light from a light source lamp placed on the backside of liquid crystal display devices and, at the same time, induces uniform light diffusion to enable clear optical images to be obtained. Background Art

[2] A light diffusion film according to the prior art is made by coating light-diffusing particles on one or both surfaces of a transparent plastic film as a substrate. The characteristics of the light diffusion film will now be described with reference to FIG. 1, which shows the light diffusion properties of the light diffusion film. Important characteristics required for the light diffusion film, which functions to transmit and uniformly diffuse light, irradiated from a light source lamp and passed through a light guide panel, without loss, include a pencil hardness of at least 2H, freedom from specks and black spots, and optical characteristics such as high haze and high total light transmittance. Such optical characteristics are measured in accordance with ASTM- D 1003, and can be calculated according to the following simple equations (see FIG. 1):

[3] Haze (HZ) (%) = DF/TT X 100;

[4] Total light transmittance (TT) (%) = light amount measured by all sensors/reference light amount X 100;

[5] Diffusion transmittance (DF) (%) = light amount measured by first and third sensors/light amount measured by all sensors X 100; and

[6] Parallel transmittance (PT) (%) = light amount measured by second sensor/light amount measured by all sensors X 100.

[7] Haze indicates the measured amount of diffused light relative to the amount of transmitted light, and is most frequently used to evaluate the performance of light diffusion films, and total light transmittance is the sum of diffusion transmittance and parallel transmittance, indicates the total amount of light passed through a sample, and is generally 90-98% for a light diffusion film. Also, diffusion transmittance is taken as a percentage obtained by dividing the measured amount of diffused light by total light transmittance. On the contrary, parallel transmittance is taken as a percentage obtained by dividing the measured amount of non-diffused light by total light transmittance. Also, Haze generally indicates 82-95% in the light diffusion film. Therefore, light diffusion films having high Haze, total light transmittance and diffusion transmittance can be considered excellent films, and light diffusion films having low parallel transmittance can be considered excellent films.

[8] However, when the light diffusion film as described above is cut, or is deposited on a backlight unit, static electricity is generated on the film, and foreign matter adheres to the film, thus causing defects in LCD devices. In the prior art, in order to impart antistatic properties to the light diffusion film during the fabrication thereof, transparent antistatic agents such as metal oxides or ions have, in some cases, been used in a light diffusion layer. However, this prior method is disadvantageous in terms of cost, because a large amount of the antistatic agent is used when the antistatic layer is thick. Also, when large amounts of antistatic agents such as metal oxides or ions are included in the light diffusion layer, they will deteriorate the characteristic optical properties of the light diffusion film, and when they are used in too small amounts, the surface resistance of the resulting light diffusion film will be excessively high, deteriorating the antistatic performance of the film. Thus, the prior method is considered to have problems. Furthermore, even when a suitable amount of the antistatic agent is used in the application of the light diffusion layer, the surface resistance of the resulting film is 10 Ω/square, which is insufficiently high to exhibit antistatic performance. Thus, there is a need to develop a light diffusion film or sheet, which has antistatic performance while maintaining or improving optical properties. Disclosure of Invention

Technical Problem

[9] The present invention has been made in view of the problems occurring in the prior art, and an object of the present invention is to provide a light diffusion film, which comprises a light diffusion layer deposited on one surface of a transparent plastic film, and an antistatic layer or a combination of an antistatic layer and a light diffusion layer, deposited on the opposite surface of the film, so that the light diffusion film prevents static electricity and foreign matter from being generated thereon and, at the same time, has improved optical properties such as haze or diffusion transmittance. Technical Solution

[10] To achieve the above object, the present invention provides a light diffusion film comprising: a transparent plastic substrate made of any one resin selected from the group consisting of polyester, polycarbonate, polymethylmethacrylate and polystyrene; a light diffusion layer formed on one surface of the substrate; and an antistatic layer formed on either a surface opposite the light diffusion layer or both surfaces of the substrate including the light diffusion layer, said antistatic layer being formed of an antistatic composition and thus having foreign matter adhesion-preventing performance, said composition containing a conductive polymer as an active ingredient.

Advantageous Effects

[11] In the above-described inventive light diffusion film for liquid crystal display devices, which comprises the transparent plastic film as a substrate, an antistatic layer 3 containing a conductive polymer as an active ingredient is formed on the surface opposite the light diffusion layer, and thus the generation of foreign matter on the film is low, static electricity is not generated on the film, and the haze of the film is high. Also, because the light diffusion layer contains no antistatic agent, the inventive light diffusion film is provided with low surface resistance at low cost, has antistatic performance and foreign matter adhesion-preventing performance, and also has improved optical properties such as haze and total light transmittance. Brief Description of the Drawings

[12] FIG. 1 illustrates the optical properties of a light diffusion film according to the present invention.

[13] FIG. 2 is a cross-sectional view showing one embodiment of the light diffusion film according to the present invention.

[14] FIG. 3 is a cross-sectional view of another embodiment of the light diffusion film according to the present invention.

[15] FIG. 4 is a cross-sectional view of still another embodiment of the light diffusion film according to the present invention.

[16] FIG. 5 is a cross-sectional view of still a further embodiment of the light diffusion film according to the present invention. Best Mode for Carrying Out the Invention

[17] In the present invention, the light diffusion layer and the antistatic layer are applied on the transparent plastic substrate, and then cured according to a method selected in consideration of the binder used in each of the light diffusion layer and the antistatic layer. For a thermosetting binder, hot air, infrared rays or far-infrared rays are irradiated onto the coating layers, and for a UV-curable binder, UV is irradiated onto the coating layers.

[18] The transparent plastic film consists of, for example, a polyester film, a polycarbonate film, a polymethylmethacrylate film, or a polystyrene film.

[19] The light diffusion layer consists of a mixture of UV-curable or thermosetting binder resin, light-diffusing particles, and the like. As the UV-curable binder resins, resins having good adhesion to the substrate and good compatibility with the light- diffusing particles are used. Preferably, UV-curable acrylate/methacrylate oligomers having 1-15 functional groups, and UV-curable acrylate/methacrylate monomers having 1-6 functional groups, are used alone or in a mixture of two or more thereof. As the thermosetting resins, resins having good adhesion to the substrate and good dis- persibility and compatibility with the light-diffusing particles are used. Such resins include unsaturated polyester resins, acrylic resins, such as methylmethacrylate, ethyl- methacrylate, isobutylmethacrylate, n-butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyethylacrylate, acrylamide, methylolacrylamide, glycidylmethacrylate, ethy- lacrylate, isobutylacrylate, n-butylacrylate, 2-ethylhexylacrylate polymers, copolymers or terpolymers, urethane resins, epoxy resins, and melamine resins. To increase the thermal resistance, wear resistance and adhesion properties of the light diffusion layer, a one-component or two-component urethane- or isocyanate-based curing agent is added to harden the resin coating film.

[20] Also, as the light-diffusing material, it is preferable to use transparent particles or white particles. Examples of transparent particles, which can be used in the present invention, include organic particles such as acrylic particles, styrene particles and silicone particles, and inorganic particles such as synthetic silica particles, glass beads and diamond particles. Also, examples of white particles, which can be used in the present invention, include titanium oxide, zinc oxide, barium sulfate, calcium carbonate, magnesium carbonate, aluminum hydroxide, and clay particles. These transparent particles or white particles can be used alone or in a mixture of two or more thereof. The particle size of the light-diffusing material is preferably about 1-50 D, and a mixture of two or more kinds of light-diffusing materials having different sizes can also be used in the present invention.

[21] As a solvent, any solvent can be used without limitation as long as it can dissolve the binder resin. Examples of such a solvent include toluene, xylene, dichloromethane, dichloroethane, methyl ethyl ketone, ethyl acetate, ethanol, methanol, and 2-propanol, and these solvents can be used alone or in a mixture of two or more thereof.

[22] Also, the antistatic layer may comprise, as active ingredients, in addition to the conductive polymer, one or a mixture of two or more selected from among doped indium oxide-, tin oxide- or titanium oxide-based metal oxides, and ionic or non-ionic surfactant-type antistatic agents. In the light diffusion film according to the present invention, a conductive polymer can be used as an active ingredient to form the antistatic layer, but another substance, if necessary, may alternatively be used as an active ingredient to form the antistatic layer.

[23] If the conductive polymer is used as an active ingredient, the antistatic layer can be formed using an antistatic composition comprising 0.05-10 wt% of the conductive polymer, 5-40 wt% of a polymer binder and 50-94.95 wt% of dispersion solvent according to a thermosetting process. Alternatively, the antistatic layer can also be formed using a composition comprising 0.05-10 wt% of the conductive polymer, 5-20 wt% of a UV-curable oligomer resin, 0-5 wt% of a UV-curable monomer resin, 0.01-0.5 wt% of a photoinitiator and 64.5-94.94 wt% of a solvent, according to the light-curing process.

[24] Preferably, the antistatic layer may comprise a conductive polymer having, for example, a thiophene, aniline or pyrrole group. Because poly(3,4-ethylenedioxythiophene), a polythiophene-based conductive polymer, has excellent transparency compared to other polymers, a composition comprising a mixture of poly(3,4-ethylenedioxythiophene) and binder resin shows excellent optical properties compared to compositions comprising other conductive polymers.

[25] As the binder, resin having good adhesion to the substrate, good dispersibility, and good compatibility with the light-dispersing particles is used. Examples of such thermosetting resin include unsaturated polyester resins, acrylic resins, such as methyl- methacrylate, ethylmethacrylate, isobutylmethacrylate, n-butylmethacrylate, n- butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyethylacrylate, acrylamide, methylolacrylamide, glycidylmethacrylate, ethylacrylate, isobutylacrylate, n-butylacrylate, 2-ethylhexylacrylate polymers, copolymers or terpolymers, urethane resins, epoxy resins, melamine resins. Examples of UV-curable resin include UV-curable aery late/ methacrylate oligomers having 1-15 functional groups and UV-curable acrylate/ methacrylate monomers having 1-6 functional groups. Such resins can be used alone or in a mixture of two or more thereof. Meanwhile, when the thermosetting binder resin is used, a one-component or two-component urethane- or isocyanate-based curing agent is added to harden the resin coating film, thus increasing the thermal resistance, wear resistance and adhesion properties of the antistatic layer. Also, to increase the electrical conductivity of the water-dispersible, conductive polymer, it is possible to add ethylene glycol, l-methyl-2-pyrrolidone or the like.

[26] In addition, the antistatic layer can also be formed by coating on the plastic substrate a mixture of an initiator and a dopant or a solution of the initiator and dopant diluted in a solvent, coating thereon a monomer for forming a conductive polymer or a solution of the monomer diluted in a solvent, and then subjecting the coated monomer to vapor phase polymerization. Alternatively, the antistatic layer can also be formed by coating on the plastic substrate a solution of the monomer, dopant and initiator, diluted in a solvent, and then polymerizing the coated monomer. However, such methods are not preferable, because the durability of the antistatic layer is low and a separate washing process is required for the residue.

[27] This antistatic layer is formed on the plastic substrate and has a surface resistance of

10E3-10E11 Ω/square. [28] Meanwhile, the prior light diffusion film is generally formed by applying the light diffusion layer on the transparent substrate layer, and thus reflection and scattering of light between the transparent substrate layer and the light diffusion layer can occur, thus reducing the haze and diffusion transmittance of the light diffusion film. Also, when antistatic treatment is performed on the light diffusion layer, it can result in a reduction in optical performance, due to the difference in refractive index from the non-uniform surface of the light diffusion layer. Therefore, it is preferable that antistatic treatment be performed on both sides of the plastic substrate in view of antistatic performance and optical performance.

[29] According to the present invention, the light diffusion layer is deposited on one surface of the transparent plastic substrate, and the antistatic layer comprising the conductive polymer is deposited on the surface opposite the light diffusion layer. The light diffusion film formed in this manner can show sufficient antistatic performance and, at the same time, can have improved optical properties, such as haze and diffusion transmittance.

[30] Hereinafter, the present invention will be described in further detail with reference to the accompanying drawings.

[31] The light transmittance of a transparent plastic substrate (2) of the light diffusion film is preferably 85-98%, and more preferably 95-98%.

[32] FIG. 2 is a cross-sectional view showing one embodiment of the light diffusion film according to the present invention. As shown in FIG. 2, a light diffusion layer 1 comprising a light-diffusing material 11 of a given size is formed on one surface of the substrate 2. Light-curing or thermosetting binder resin for use in the light diffusion layer 1 should be transparent and can be any one or a mixture of two or more selected from among acrylic resins such as polymethylmethacrylate or methacrylic ester copolymers, urethane resins, epoxy resins, vinyl resins, polyester resins, and polyamide resins.

[33] Also, the thickness of the light diffusion layer 1 is preferably in the range of 1-50 D.

If the thickness of the light diffusion layer 1 is less than 1 D, the application of the light- diffusing material 11 will not be easy, and the haze of the layer will not be high, making it difficult to obtain highly uniform light in a backlight unit, and if the thickness is more than 50 D, the light transmittance of the light diffusion film will be reduced, making it difficult to achieve high brightness in a backlight unit.

[34] Also, in order to prepare a light diffusion film for use in liquid crystal display devices having predetermined ranges of optical properties, it is important to suitably control the ratio between the binder resin and the light-diffusing material. Particularly, in order to prepare a light diffusion film having a total light transmittance of 90-100 %, it is preferable that the ratio of the light-diffusing material to the binder resin be 20-300 wt%. If the ratio of the light-diffusing material to the binder resin is less than 20 wt%, it will be difficult to obtain excellent light diffusion properties due to low haze, and if the ratio is more than 300 wt%, total light transmittance will be reduced, making it difficult to obtain a light diffusion film having high light transmittance.

[35] Meanwhile, the thickness of the antistatic layer 3 applied opposite the transparent plastic substrate 2 is preferably 0.01-1 D. If the thickness of the antistatic layer comprising the conductive polymer/binder resin mixture is more than 1 D, the resulting film cannot be used as a light diffusion film for backlight units due to the characteristic color of the conductive polymer.

[36] FIG. 3 is not different in configuration from FIG. 2, but shows that light-diffusing material 12 having a size different from that of the light-diffusing material 11 was deposited during the preparation of the light-diffusing layer 1. When the light-diffusing material 11 having a relatively large size and the light-diffusing material 12 having a relatively small size are mixed at a given weight ratio (about 7:3) and applied on the substrate, the light diffusion ability of the light diffusion layer can be increased, because the amount of the light-diffusing material per unit area is increased.

[37] FIG. 4 shows that a small amount of a light-diffusing material 15 having a small particle size was added to the antistatic layer 3. When the light-diffusing material 15 is used as shown in FIG. 4, the resulting light diffusion film can have increased light diffusion ability, because light is passed through the two light diffusion layers from a light source.

[38] FIG. 5 shows the combination of the structure of FIG. 3 and the structure of FIG. 4.

As shown in FIG. 5, the light-diffusing materials 11 and 12 having different particle sizes are deposited on the light diffusion layer 1 to increase the ratio of the light- diffusing materials per unit area, and the light-diffusing material 15 is added to the antistatic layer, so that two-step light diffusion from a light source can be achieved.

[39] The method of applying the light diffusion layer and the antistatic layer is not specifically limited as long as it is generally known in the art to which the present invention pertains. Depending on the material and shape of the substrate film, the application method can be optionally selected from among an air-knife process, a gravure process, a reverse roll process, a reverse gravure process, a spray process, and a blade process.

[40] In the above embodiments according to the present invention, the ratio of thickness between the transparent plastic substrate 2, the light diffusion layer 1, and the antistatic layer 3 deposited opposite the light diffusion layer is preferably 5000-20000 : 500-5000 : 0.1-10 in view of optical properties.

[41] The inventive light diffusion film as described above shows increases of more than

2% in optical properties, compared to the prior light diffusion film, which shows a total light transmittance of 85-95% and a haze of 82-95%. In other words, the light diffusion film according to the present invention can have a total light transmittance of 85-100% and a haze of 82-98% in optical properties. Mode for the Invention

[42] Table 1 below shows the comparison of total light transmittance, haze, surface resistance and scratch resistance between light diffusion films according to Examples 1 to 16 and light diffusion films according to Comparative Examples 1 and 2.

[43] Total light transmittance and haze were measured with NDH-2000 (Nippon

Denshoku) in accordance with ASTM D- 1003. Also, the surface resistance of the antistatic layer was measured with SRM-100 in accordance with ASTM D-257. Moreover, the pencil hardness of the light diffusion layer was measured, in which a pencil hardness of 2H or more was judged to be good, and a pencil hardness lower than 2H was judged to be bad. Moreover, the tribo- voltage of an antistatic layer was measured with the static sensor 718A (3M Co.). Generally, a tribo- voltage of less than 100V is judged to be good, and a tribo-voltage of more than 100V is judged to be bad. Meanwhile, decay time was measured with the charge plate monitor CPM288 (MONROE ELECTRONICS). For the measurement of decay time, 1050V was applied to the samples, and the time taken for the charging voltage to decay below 100V was noted. Generally, a decay time of more than 3 seconds is judged to be bad, and a decay time of less than 3 seconds is judged to be good.

[44] Table 1

[45] As can be seen in Table 1 above, in the case of Examples 1-16, where an antistatic layer, consisting of poly(3,4-ethylenedioxythiophene) and a binder, was applied on one surface of the transparent plastic substrate 2, total light transmittance and haze were increased by about 2% compared to Comparative Examples 1 and 2. Also, when a UV- curable binder resin was used, the light diffusion layer had excellent hardness. In addition, the antistatic coating made it possible to prepare a light diffusion film having low tribo- voltage and a short decay time.

[46] Hereinafter, the present invention will be described in further detail with reference to examples. It is to be understood, however, that these examples are not to be construed to limit the scope of the present invention. In the following examples, either the light diffusion layer or the antistatic layer may be applied first in sequence.

[47] Comparative Example 1

[48] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a light-diffusing material (MX-1000, Soken), 0.6 g of a photoinitiator and 3 g of toluene were mixed with each other to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic substrate 2 using a bar coater and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. [49] Comparative Example 2

[50] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a light-diffusing material

(MX-1000, Soken) and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D.

[51] Example 1

[52] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a light-diffusing material

(MX-1000, Soken) having a diameter of 10 D and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic film 2 using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of a poly(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol, and 3 g of water were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D.

[53] Example 2

[54] 1 g of a thermosetting acrylic polyol binder resin, 1.75 g of a light-diffusing material having a diameter of 10 D (MX-1000, Soken) and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light-diffusing layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) diluted in 5 g of iso- propylene alcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator and 1.5 g of methylcellosolve to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[55] Example 3

[56] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of UV-curable diacrylate monomer resin, 1.75 g of a light-diffusing material (MX-1000, Soken), 0.6 g of a photoinitiator and 3 g of toluene were mixed with each other to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic film 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator and 1.5 g of methylcellosolve to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 0.1 D.

[57] Example 4

[58] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a light-diffusing material (MX-1000, Soken) and 0.6 g of a photoinitiator were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic film 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of a pol y(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol and 3 g of water were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D.

[59] Example 5

[60] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of poly(3,4-ethylenedioxythiophene) dispersion, 0.3 of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol and 3 g of water were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D.

[61] Example 6

[62] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator and 1.5 g of methylcellosolve to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[63] Example 7

[64] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a photoinitiator were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator and 1.5 g of methylcellosolve to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[65] Example 8

[66] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer resin, 0.15 g of a photoinitiator and 1.5 g of methylcellosolve to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[67] Example 9

[68] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a light-diffusing material (MX-1000, Soken) and 0.6 g of a photoinitiator (CP4, Miwon Commercial Co., Ltd.) were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of poly(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water- soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol, 3 g of water and 0.3 g of a light- diffusing material (MX- 150, Soken) were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D.

[69] Example 10

[70] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a 10-D diameter light- diffusing material (MX-1000, Soken) and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator, 1.5 g of methylcellosolve and 0.3 g of a light-diffusing material (MX- 150, Soken) to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[71] Example 11

[72] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a light-diffusing material (MX-1000, Soken) and 0.6 g of a photoinitiator were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a plastic film as the transparent plastic film 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator, 1.5 g of methylcellosolve and 0.3 g of a light-diffusing material (MX- 150, Soken) to prepare an antistatic composition. The prepared antistatic composition was applied on a surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[73] Example 12

[74] 1 g of UV-curable aliphatic 6-functional urethane acrylate oligomer binder resin,

0.3 g of UV-curable diacrylate monomer binder resin and 1.75 g of a light-diffusing material (MX-1000, Soken) and 0.6 g of a photoinitiator were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a plastic film as the transparent plastic substrate 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of poly(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol, 3 g of water and 0.3 g of a photoinitiator (MX- 150, Soken) were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on a surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic composition having a thickness of about 0.1 D.

[75] Example 13

[76] 1 g of thermosetting acrylic polyol binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a polyisocyanate curing agent, were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of poly(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol, 3 g of water and 0.3 g of a light-diffusing material (MX- 150, Soken) were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D.

[77] Example 14

[78] 1 g of thermosetting acrylic polyol binder resin, 1.75 of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a polyisocyanate curing agent were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a 100-D polyester film as the transparent plastic substrate using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion dissolved in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator, 1.5 g of methylcellosolve and 0.3 g of a light-diffusing material (MX- 150, Soken) to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[79] Example 15

[80] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000 Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a photoinitiator, were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, a solution of 1 g of poly(3,4-ethylenedioxythiophene) dispersion diluted in a mixture of 5 g of iso- propylalcohol and 5 g of methylcellosolve was mixed with 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.35 g of UV-curable diacrylate monomer binder resin, 0.15 g of a photoinitiator, 1.5 g of methylcellosolve and 0.3 g of a light-diffusing material (MX- 150, Soken) to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming an antistatic layer having a thickness of about 0.1 D.

[81] Example 16

[82] 1 g of UV-curable 6-functional urethane acrylate oligomer binder resin, 0.3 g of

UV-curable diacrylate monomer binder resin, 1.75 g of a mixture of a 10-D diameter light-diffusing material (MX-1000, Soken) and a 3-D diameter light-diffusing material (MX-300, Soken) (7:3 w/w), and 0.6 g of a photoinitiator (CP4, Miwon Commercial Co., Ltd.), were mixed with 3 g of toluene to prepare a light diffusion layer composition. The composition was applied on one surface of a polyester film as the transparent plastic substrate 2 using a bar coater, and then dried at 60 ⁰C for 1 minute, followed by UV curing, thus forming a light diffusion layer having a thickness of about 15 D. Meanwhile, 1 g of poly(3,4-ethylenedioxythiophene) dispersion, 0.3 g of a water-soluble urethane binder, 0.03 g of a urethane curing agent, 0.3 g of ethylene glycol, 0.3 g of l-methyl-2-pyrrolidone, 5.5 g of 2-propanol, 3 g of water and 0.3 g of a light-diffusing material (MX- 150, Soken) were mixed with each other to prepare an antistatic composition. The prepared antistatic composition was applied on the surface opposite the light diffusion layer using a bar coater, and then dried at 80 ⁰C for 2 minutes, thus forming an antistatic layer having a thickness of about 0.1 D. Industrial Applicability

[83] The light diffusion film according to the present invention transmits light from a light source lamp placed on the backside of liquid crystal display devices such as LCD panels and, at the same time, induces uniform light diffusion to enable clear optical images to be obtained.

Claims

[1] A light diffusion film having improved total light transmittance and haze, the film comprising: a transparent plastic substrate made of any one resin selected from the group consisting of polyester, polycarbonate, polymethylmethacrylate and polystyrene; a light diffusion layer formed on one surface of the substrate; and an antistatic layer formed on a surface opposite the light diffusion layer, said antistatic layer being formed of an antistatic composition and thus having antistatic performance and foreign matter adhesion-preventing performance, said composition containing a conductive polymer as an active ingredient.

[2] The light diffusion film of Claim 1, wherein the light diffusion layer comprises at least two kinds of light-diffusing materials having different sizes.

[3] The light diffusion film of Claim 1 or 2, wherein the antistatic layer comprises a light-diffusing material.

[4] The light diffusion film of any one of Claims 1 to 3, wherein the composition comprises: the conductive polymer; and a UV-curable binder, a thermosetting binder or a mixture thereof.

[5] The light diffusion film of any one of Claims 1 to 4, wherein the conductive polymer is one or more selected from the group consisting of polyaniline, polypyrrole, polythiophene and poly(3,4-ethylenedioxythiophene).

[6] The light diffusion film of any one of Claims 1 to 5, wherein the composition comprises a UV-curable binder, which has good adhesion to the substrate and good compatibility with light-diffusing particles and is one or a mixture of two or more selected from the group consisting of UV-curable acrylate/methacrylate oligomers having 1-15 functional groups and UV-curable acrylate/methacrylate monomers having 1-6 functional groups.

[7] The light diffusion film of Claim 6, wherein the composition comprises 0.05-10 wt% of the conductive polymer, 5-20 wt% of UV-curable oligomer resin, 0-5 wt% of UV-curable monomer resin, 0.01-0.5 wt% of a photoinitiator, and 64.5-94.94 wt% of a solvent, and is formed into the light diffusion layer using a light curing method.

[8] The light diffusion film of any one of Claims 1 to 5, wherein the composition comprises 0.05-10 wt% of the conductive polymer, 5-40 wt% of a thermosetting binder and 50-94.95 wt% of a dispersing solvent, and is formed into the light diffusion layer using a thermosetting method.

[9] The light diffusion film of Claim 8, wherein the binder is one or a mixture of two or more selected from the group consisting of unsaturated polyester resins, acrylic resins such as methylmethacrylate, ethylmethacrylate, isobutyl- methacrylate, n-butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hy- droxyethylacrylate, acrylamide, methylolacrylamide, glycidylmethacrylate, ethy- lacrylate, isobutylacrylate, n-butylacrylate, 2-ethylhexylacrylate polymers, copolymers or terpolymers, urethane resins, epoxy resins, and melamine resins.

[10] The light diffusion film of any one of Claims 1 to 9, wherein the ratio of thickness between the transparent plastic substrate, the light diffusion layer and the antistatic layer deposited on the surface opposite the light diffusion layer is 5000-20000 : 500-5000 : 0.1-10.

[11] The light diffusion film of any one of Claims 1 to 10, wherein a method of coating the light diffusion layer and the foreign matter adhesion-preventing and antistatic layer on the transparent plastic substrate is performed either by coating one side of the substrate and then coating the opposite side of the substrate, or by simultaneously coating both sides of the substrate, using an air knife process, gravure process, reverse roll process, reverse gravure process, spray process or blade coating process.

[12] The light diffusion film of any of Claims 1 to 11, wherein the antistatic layer coated on the plastic substrate and comprising the conductive polymer has a surface resistance of 10E3-10E11 Ω/square.

[13] The light diffusion film of any one of Claims 1 to 12, wherein the antistatic layer coated on the plastic substrate and comprising the conductive polymer reduces tribo-voltage below 100 V.

[14] The light diffusion film of any one of Claims 1 to 13, wherein the antistatic layer is formed to a thickness of 0.01-2 microns.

[15] The light diffusion film of Claim 1, wherein the antistatic layer comprises, besides the conductive polymer, one or a mixture of two or more selected from among doped indium oxide-, tin oxide- and titanium oxide-based metal oxides and ionic and non-ionic surfactant-type antistatic agents.