WO2010126182A1 - Light diffusing sheet for lcd backlight unit - Google Patents

Abstract

The present invention relates to a light diffusing sheet for an LCD backlight unit, and more specifically to a light diffusing sheet wherein a nonwoven fabric, a nonwoven fabric with a planarized surface or a laminated nonwoven fabric with transparent film, is used as a substrate to form a light diffusing layer on either the front or back surface of the diffusing sheet, thereby enabling high light-shielding effect and luminance compensation. The substrate for the light diffusing sheet for LCD backlights, according to the present invention, comprises a nonwoven fabric and a light diffusing layer coated on at least one surface of the substrate with a coating liquid including a binder resin and transparent spherical particles, whereby said substrate is preferably laminated to a transparent polyethyleneterephthalate film. In addition, the nonwoven fabric alone, or an optical molded or processed nonwoven fabric, is used as the substrate, or part of the substrate for, of the diffusing sheet for a backlight unit.

Description

Light Diffusion Sheet for LCD Backlight Unit

The present invention relates to a light diffusing sheet for an LCD backlight unit, and more particularly, a light diffusing layer on at least one of a surface and a back surface of a non-woven fabric or a surface of a non-woven fabric, or a laminate of a nonwoven fabric and a transparent film. The present invention relates to a light diffusion sheet for an LCD backlight unit, which provides high shielding characteristics and is capable of luminance compensation by the formed light diffusion layer.

Generally, the light diffusion sheet for LCD backlight has a linear lamp on one side of the light guide plate, which is used in small size such as car navigation system, mobile phone, PDA, digital camera, portable TV, camcorder, etc. In an EDGE type backlight unit and a SIDE type backlight unit in which one or more lamps are installed and used, a non-uniform light source from a light guide plate is converted into a uniform light centered on the front of the backlight unit. Even in the case of the direct type, which is used in TVs or some large-sized monitors, in the case of a large number of cold-cathode fluorescent lamps or flat lamps installed on the back of the backlight, the linearly visible light is diffused to provide a uniform omnidirectional central distribution. It performs the function of surface light source and converts the center of light distribution to the front direction. From comes the effect of increasing the luminance in the front direction.

In order to perform the shielding function and the diffusion function and to improve the brightness in the function of the light diffusion sheet for the LCD backlight, a method of applying transparent organic resin particles or inorganic particles on a transparent plastic film with a transparent resin binder has been developed.

However, the conventional techniques as described above do not satisfy the performance of the brightness and shielding function required for high efficiency backlight such as thinning and low power consumption.

The present invention has been made to solve the above problems, an object of the present invention by using a non-woven fabric as a substrate or a part of the substrate to replace the conventional light diffusion film that is conventionally applied to form a light diffusion layer on at least one side of the substrate It is an object of the present invention to provide a light diffusing sheet for an LCD backlight unit and a sheet for a backlight unit that maximize shielding and scattering effects of light.

These and other objects and advantages of the present invention will become more apparent from the following description of preferred embodiments.

The object is a light diffusion sheet for an LCD backlight unit, comprising: a substrate made of a nonwoven fabric as a substrate and a light diffusion layer coated on at least one surface of the substrate with a coating liquid containing a binder resin and spherical transparent particles; A light diffusing sheet sheet for an LCD backlight unit is achieved.

Preferably, the substrate is characterized in that the non-woven fabric and at least one transparent film selected from a transparent polyethylene terephthalate, polycarbonate, polypropylene, polyisulfone and polyimide film is laminated.

Also preferably, the base material may have at least one surface of the nonwoven fabric alone in resins such as acrylic, urethane, epoxy, vinyl, polyester, and polyimide resins such as polymethyl methacrylate or methacrylic acid ester copolymers. Or a substrate having a planarization coating treatment by mixing two or more kinds thereof and coating the light diffusing layer on a surface of the planarization coating treatment.

More preferably, the nonwoven fabric has an unbonding rate of 0% to 85%, a weight of 10 to 100g / m ² , and the material of the nonwoven fabric is polypropylene (PP) or polyethylene terephthalate (PET).

More preferably, the spherical transparent particles of the light diffusion layer is characterized in that the particles are mixed at least one or more of monodisperse particles, polydisperse particles and polydisperse particles.

More preferably, the refractive index of the spherical transparent particles of the light diffusion layer is 1.4 to 1.6, the spherical transparent particles is characterized in that the use of two or more particles having a single or different refractive index.

More preferably, it further comprises an antistatic layer on the opposite side of the sheet on which the light diffusion layer is formed.

According to the present invention, a non-woven fabric itself or a non-woven fabric laminated on a transparent film or a non-woven fabric flattened surface is used, and at least one surface of the substrate is light-diffused coating, thereby slimming the backlight and reducing the number of lamps, LED point light source This can effectively solve the problem of the visual perception caused by the.

Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples. .

The light diffusing sheet for an LCD backlight unit according to the present invention relates to a light diffusing sheet used in a backlight unit of an LCD, and more particularly, a thin film transistor liquid crystal display (TFT-LCD) or a super twisted nematic liquid crystal display (STN-LCD). A light diffusion sheet used for), which induces uniform surface light and obtains high brightness and clear light image while passing light from linear light emitted from a cold cathode fluorescent lamp located on the side or the back to obtain a clear image of the display. It relates to a light diffusion sheet that can be.

The light diffusing sheet for an LCD backlight unit according to the present invention is characterized in that it comprises a light diffusion layer coated with a substrate and a coating liquid containing a binder resin and spherical transparent particles on at least one surface of the substrate, the substrate is a non-woven fabric itself Or at least one surface of the nonwoven fabric coated with a binder or flattened, or at least one transparent film selected from a nonwoven fabric and a transparent polyethylene terephthalate, polycarbonate, polypropylene, polyisulfone, and polyimide film is laminated. . Here, at least one surface of the nonwoven fabric is coated with a binder to flatten the base material of at least one surface of the nonwoven fabric, such as polymethyl methacrylate or methacrylic acid ester copolymer, such as acrylic, urethane, epoxy, vinyl, polyester, It is a planarized coating by coating alone or in mixture of two or more kinds of resin such as polyimide-based, and then the light diffusion layer is applied to the flattened coated surface.

The light diffusing sheet for an LCD backlight unit according to the present invention is characterized in that the nonwoven fabric is used as a base material or a part of the base material. This is because it is possible to enhance the shielding force and at the same time increase the luminance by forming a light diffusion layer on at least one surface.

The nonwoven fabric has basic properties of 50 to 95% haze and 30 to 80% transmittance, and properties of the final light diffusion sheet having a light diffusion layer formed on at least one surface of the nonwoven fabric also have a haze of 50 to 95% and transmittance 30 to 80%. Has

In addition, the nonwoven fabric according to the present invention has an unbonding rate of 0% to 85%, preferably 10 to 100 g / m ² , and the material of the nonwoven fabric is preferably polypropylene (PP) or polyethylene terephthalate (PET). Do.

If the non-bonding rate of the nonwoven fabric is greater than 85% (less than 15% bonding rate), the formed web may have insufficient form stability and low strength, and thus may not be applied as a cloth, and the nonwoven fabric may have a weight of 10 g / m 2. If it is less than one, there is a disadvantage in that it is not economically produced, such as a decrease in productivity, and if the weight exceeds 100 g / m 2, it is too thick, so that heat transfer is difficult in performing heat calendering to give form stability. This is because there is a problem that becomes difficult.

The binder resin used in the light diffusing layer of the light diffusing sheet for LCD backlight unit according to the present invention should be transparent and acrylic, urethane, epoxy, vinyl, polyester, such as polymethyl methacrylate or methacrylic acid ester copolymer. And it can use individually or in mixture of 2 or more types in resin, such as a polyimide system.

In addition, the transparent particles used as the light diffusing agent are preferably spherical, and as such transparent particles, organic particles such as acrylic particles, styrene particles, silicon particles, and inorganic particles such as synthetic silica, glass beads, and diamond may be used. These light diffusing agents can be used individually or in mixture of 2 or more types.

In addition, the spherical transparent particles are characterized in that the particles are at least one of a mixture of monodisperse particles, polydisperse particles and polydisperse particles. Here, "monodispersion particles, polydispersion particles and polydispersion particles" are divided according to the particle size distribution of the particles. For example, when 10 micrometers monodisperse particle | grains are divided into monodispersion when the particle content rate of 10 micrometers of average particle diameters is 90% or more, it is divided into polydispersion when it is 80% or more, and polydispersion when it is less than that.

In addition, the refractive index of the spherical transparent particles is 1.4 to 1.6, it is preferable that the particles are used alone or two or more particles having different refractive index. When the refractive index of the spherical transparent particles is out of the range of 1.4 ~ 1.6, that is, when the refractive index is less than 1.4 or more than 1.6, it is generally possible to manufacture it by changing to another material (inorganic), not the material of the particles used in the light diffusion film. In this case, the refractive index is most preferably in the above range because the light absorbing light is not suitable for use for the optical sheet and there is a problem that the price is increased.

As a method of manufacturing the light diffusion sheet according to the present invention, various coating methods such as a conventional wet coating method such as a knife coating method, a gravure transfer coating method, a reverse roll coating method, and other deposition methods may be applied.

In addition, the back surface of the light diffusing layer formed on one surface of the light diffusing sheet according to the present invention (opposite side of the light diffusing sheet having the light diffusing layer) is provided with a slip property, and the hardness for suppressing the scratches generated during the cutting and assembly operations It is also possible to form an antistatic layer having an antistatic function for the purpose of preventing the incorporation of foreign matters.

The light diffusion sheet manufactured according to the present invention has improved light shielding performance than the conventional light diffusion sheet when mounted in the backlight unit.

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

In the light diffusing sheet having the light diffusing layer formed in the following Examples and Comparative Examples, the light diffusing layer was formed with the same coating solution, and the shielding force according to the substrate using the nonwoven fabric and the general transparent film (PET) substrate was compared. After the planarization coating process using resin, the light-diffusion layer was formed on it, and the sample which formed the light-diffusion layer on one surface was compared and evaluated based on what laminated | stacked the nonwoven fabric and general transparent film (PET). In the following, "paper calendaring" means heat pressing on one side of a nonwoven fabric as is well known to those skilled in the art.

 Example 1

A coating solution 1 having the following composition was applied to a non-woven fabric of 85% of a paper calendaring-treated non-bonding ratio and a weight of 30 g / m ² by using microgravure to form a light diffusion layer.

Composition of Coating Liquid 1

Binder (acrylic urethane, A-811): 18% by weight

Solvent (MEK): 50 wt%

Particle 1 (10 μm medium dispersion, MH-10FD): 20 wt%

Particle 2 (5 μm polydispersity, MH-5FD): 9 wt%

Curing agent (isocyanate): 2% by weight

-Additive (silicone Wetting agent): 1% by weight

Example 2

Paper knife rendered (Paper calendaring) by a coating liquid 2 having the following composition in the non-woven fabric of the treated non-bonding rate of 85% by weight 30 g / m ² treated planarized by coating using a microgravure then, the same as in Example 1 Coating solution 1 was applied to the flattened coated surface using microgravure.

Composition of Coating Liquid 2

Binder Resin (A-811): 70 wt%

Solvent (MEK): 20 wt%

Curing agent (isocyanate): 8% by weight

-Additive (silicone Wetting agent): 2% by weight

Example 3

Non-woven fabric with a weight of 30 g / m ² , 85% of unbonded paper calendaring, and a transparent PET film (XU42) generally used in the manufacture of diffused films having a haze of about 1% and a transmittance of about 92%. The same coating liquid 1 as in Example 1 was applied onto the PET film by laminating with an acrylic adhesive using microgravure.

[Comparative Example]

The same coating solution 1 as in Example 1 was applied to one surface of the transparent PET film (XU42) using microgravure.

Evaluation was carried out using the light diffusing sheets prepared by the above Examples and Comparative Examples through the following evaluation method and the results are shown in Table 1 below.

[Assessment Methods]

-HAZE was measured according to ASTM D-1003, and the measuring instrument was NIPPON DENSHOKU KOGYO Co. Ltd. Ltd. Model 1000 was used.

The luminance was compared by measuring the front luminance value on the backlight assembly using Topcon's BM-7A measuring instrument (Sample Structure: Sample // Prism).

-The shielding force was quantified by defining the front brightness of the backlight assembly at equal intervals 100 points by using Topcon's BM-7A measuring device as shown in Equation 1 below.

[Equation 1]

Table 1

.	Properties					Comprehensive evaluation
unit	Haze	Transmittance	After	Luminance	Shielding force
	%	%	Μm	%	%
Example 1	87.23	43.85	110.0	93.7	8.4	Great
Example 2	87.43	58.72	110.1	94.3	10.7	Great
Example 3	87.40	50.94	110.1	96.6	9.2	Great
Comparative example	85.87	67.54	110.1	100.0	23.9	Standard

As can be seen in Table 1, in the case of Examples 1 to 3 in which the non-woven fabric itself or the surface of the non-woven fabric according to the present invention is used as a substrate or the non-woven fabric is laminated to a general transparent film as a substrate, the general transparent film It can be seen that the shielding force is much better than the sheet according to the comparative example in which the diffusion layer is formed on the substrate. In addition, as can be seen in Examples 2 and 3, the use of a flattened coating of nonwoven fabric as a base material or a non-woven fabric laminated on a transparent film as a base material forms a light diffusion layer thereon, which is more effective in increasing luminance. It can be seen that.

The above examples are intended to illustrate the present invention in detail, and do not limit the scope of the present invention, all of the simple modifications or variations of the present invention can be seen to be included in the scope of the present invention.

Claims (7)

1. In the light diffusion sheet for LCD backlight unit,

   Base material consisting of nonwoven fabric as base material

   And a light diffusion layer coated on at least one surface of the substrate with a coating liquid containing a binder resin and spherical transparent particles.
2. The method of claim 1,

   The substrate is a light diffusion sheet for an LCD backlight unit, characterized in that the non-woven fabric and at least one transparent film selected from a transparent polyethylene terephthalate, polycarbonate, polypropylene, polyisulfone and polyimide film is laminated.
3. The method of claim 1,

   The said base material mixes at least one surface of the said nonwoven fabric individually or 2 or more types in resin, such as acrylic, urethane, epoxy, vinyl, polyester, polyimide, etc., such as a polymethyl methacrylate or a methacrylic acid ester copolymer, etc. By coating to form a flattening coating

   The light diffusion layer is a light diffusion sheet for an LCD backlight unit, characterized in that applied to the planarized coating surface.
4. The method according to any one of claims 1 to 3,

   The nonwoven fabric has an unbonding rate of 0% to 85%, a weight of 10 to 100g / m ² ,

   The material of the nonwoven fabric is polypropylene (PP) or polyethylene terephthalate (PET), characterized in that the light diffusion sheet for LCD backlight unit.
5. The method of claim 4, wherein

   The spherical transparent particles of the light diffusion layer is a light diffusion sheet for an LCD backlight unit, characterized in that the particles are at least one of a mixture of mono-dispersed particles, polydispersed particles and polydisperse particles.
6. The method of claim 4, wherein

   The refractive index of the spherical transparent particles of the light diffusing layer is 1.4 to 1.6, the spherical transparent particles are characterized in that the light diffusion sheet for the LCD backlight unit using two or more particles having a different or different refractive index.
7. The method according to any one of claims 1 to 3,

   And an antistatic layer on an opposite surface of the sheet on which the light diffusing layer is formed.