KR100582185B1 - The light-diffusing film and composition for the same - Google Patents

Abstract

The present invention relates to a light-diffusion film composition and a light-diffusion film using the composition, which improves the luminance characteristic and improves the luminance uniformity because it hardly generates an electrostatic spot.

The composition for a light diffusion film of the present invention comprises 100 parts by weight of a binder resin, 10 to 500 parts by weight of a light diffusing agent, and 30 to 500 parts by weight of an organic solvent, and has a volume resistivity of 1 × 10 ¹³ Pacm or less.

The light diffusing film obtained by using the composition has a volume resistivity of 1 × 10 ¹³ Ωcm or less, so that no electrostatic spots are generated, and thus the appearance is clean, and the luminance characteristics and luminance uniformity are suitable for various image display devices.

Description

The light-diffusing film and composition for the same}

The present invention relates to a light diffusing film composition and a light diffusing film using the same, in particular, the appearance is clean because the electrostatic spot does not occur, excellent brightness characteristics and brightness uniformity, light diffusion suitable for application to various image display devices It relates to a film composition and a light diffusing film using the same.

As the industrial fields are diversified, polymer resin films have a wide range of applications such as packaging, photographic films, capacitors, electrical insulation materials, labels, magnetic recording media, and medical applications. It is expanding to the field of image display devices such as plasma display panels and liquid crystal display devices.

In particular, the display method of the image display device is an indirect illumination method that displays an image through a light guide plate by reflecting light generated from a fluorescent tube of a backlight attached to the back of the device, unlike a cathode ray, to a metal deposition layer or a white plate. There is a problem that is difficult to see, and the situation is getting deeper according to the trend of increasing the size of the image display device.

In order to overcome this problem, a light diffusing film has been developed that can increase brightness by bonding light on a light guide plate and spreading light uniformly. For example, Japanese Patent Laid-Open Nos. Hei 6-67003, Hei 7-174909 and Hei 9-127314, etc., show inorganic or organic particles as a light diffusing agent on one side of a transparent polymer resin film and a transparent binder resin. A light diffusion film coated with a solution dispersed in an organic solvent together has been proposed.

However, the light diffusing film formed as described above has not only a satisfactory level of excellent optical characteristics such as high luminance, but also has a problem in that luminance uniformity showing uniform luminance over the entire surface is somewhat lowered.

In order to satisfy the luminance uniformity, it is also important to sufficiently disperse the organic or inorganic light diffusing agent in the light diffusing layer. Uniformity cannot be met.

In particular, the polymer resin used as the substrate has difficulty in forming a uniform coating due to the high electrical resistivity, and when the applied light diffusing layer is dried, a bird-shaped or oval coating called an electrostatic spot is formed on the surface of the light diffusing layer. Not only does the unevenness cause poor appearance, but also causes a problem that the brightness is lowered and the brightness uniformity is also significantly lowered.

The technical problem to be achieved by the present invention is to provide a composition for an optical film having improved luminance characteristics and improved luminance uniformity because almost no electrostatic spots are generated.

Another technical problem to be achieved by the present invention is to provide a light diffusion film obtained by coating the composition.

Another technical problem to be achieved by the present invention is to provide a backlight or LED lamp for LCD obtained by employing the light diffusion film.

In order to achieve the above technical problem, the present invention comprises 100 parts by weight of a binder resin, 10 to 500 parts by weight of a light diffusing agent, and 30 to 500 parts by weight of an organic solvent, and has a volume resistivity of 1 × 10 ¹³ Ωcm or less. Provided is a composition for diffusion films.

It is preferable that the volume resistivity of the organic solvent used for the said composition is 5 * 10 <^12> cm <3> or less.

Organic solvents having a volume resistivity of 5 x 10 ¹² Ωcm or less used in the composition are, for example, toluene, dichloroethane, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, ethyl acetate, n-butyl acetate, One or more selected from the group consisting of xylene, cyclohexane, tetrahydrofuran, n-heptane and cellulsolveacetate.

The binder resin used in the composition is not particularly limited as long as it is commonly used for producing a light diffusion film, and for example, polyvinyl alcohol, ethylene vinyl copolymer, acrylic resin, polyester resin, styrene resin, alkyd Resins, amino resins, polyurethane resins, epoxy resins and the like.

As the light diffusing agent used in the composition, inorganic or organic light diffusing agents may be used alone or in combination. Examples of the inorganic light diffusing agents include silica, zirconia, calcium carbonate, barium sulfate, titanium oxide, and the like. Examples of the organic light diffusing agent include homopolymers obtained by using monomers such as propylene, vinylidene chloride, acrylonitrile, methyl (meth) acrylate, styrene and urethane, or copolymers of these monomers.

The light diffusion film composition may further include various additives commonly used as a curing agent, an antistatic agent, a leveling agent, or a wetting agent, and the amount of the additives may be 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin. desirable.

In order to achieve another technical problem of the present invention, the present invention provides a light diffusing film obtained by applying the composition for the light diffusing film.

In order to achieve another technical problem of the present invention, the present invention provides a backlight or LED lamp for LCD employing the light diffusion film.

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

In general, the formation of the light diffusing layer uniformly on the substrate is affected by a variety of process conditions, but the binder resin and light diffusing agent composed of an organic polymer having a volume resistivity of 1 × 10 ¹³ Ωcm or more, in particular During the operation, the electrostatic spot is generated on the surface of the light diffusing layer by drying and acts as a cause of generating static electricity between the substrate and the substrate. In addition, the appearance is poor, the luminance is lowered, and the luminance uniformity is also significantly lowered.

Since the electrostatic spot is generated before the composition containing the organic solvent is applied to the substrate or dried after the coating, the electrostatic spot can be significantly reduced by controlling the volume resistivity of the composition for the entire light diffusion film.

The present inventors have confirmed that the above-mentioned electrostatic spot mainly occurs when the volume resistivity of the composition for the light diffusion film exceeds 1 × 10 ¹³ Ωcm, thus controlling the volume resistivity of the composition to 1 × 10 ¹³ Ωcm or less. It is most important to do.

In the present invention, by using an organic solvent having a volume resistivity of 5 × 10 ¹² cm 3 or less, it is possible to control the volume resistivity of the composition to 1 × 10 ¹³ cm 3 or less. When the volume resistivity of the organic solvent exceeds 5 × 10 ¹² cm 3, the volume resistivity of the composition including the same exceeds 1 × 10 ¹³ cm 3, which is not preferable since an electrostatic spot is generated.

Examples of the organic solvent having a volume resistivity of 5 × 10 ¹² μm or less as described above include toluene, dichloroethane, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, ethyl acetate, n-butyl acetate, and xylene And at least one selected from the group consisting of cyclohexane, tetrahydrofuran, n-heptane and cellussolve acetate, preferably a mixed solvent of toluene and methyl ethyl ketone, a mixed solvent of toluene and cyclohexanone, or n-butyl Acetate is exemplified. These volume resistivities are listed in Table 1 below, and they may exhibit a desired volume resistivity of 5 × 10 ¹² Ωcm or less by mixing alone or in combination of two or more.

Table 1

In the solvent, methyl ethyl ketone, methyl isobutyl ketone, n-butyl acetate, cyclohexanone, and cellulsolve acetate were used as the solvent of the composition for the light diffusion film alone as 5 × 10 ¹² cm 3 or less, considering only the volume resistivity. Although it can be used without particular limitation because it is a solvent that does not generate static electricity, in consideration of paint properties such as volatility, solubility, dispersibility and leveling, it is also preferable to use in combination with other solvents.

Toluene, cyclohexane, or n-heptane, which is inexpensive compared to other solvents and has high solubility, have a volume resistivity of more than 5 × 10 ¹² Ωcm, which can cause electrostatic spots when used alone. When used in combination with other solvents such as hexanone, the volume resistivity can be lowered to 5 × 10 ¹² cm 3, which can be used as the organic solvent of the present invention.

The method of manufacturing a light diffusing film using the composition for a light diffusing film as described above may be carried out in accordance with a conventional film production method, the volume resistivity of the light diffusing agent, the binder resin and a small amount of additives is 5 × 10 ¹² Ωcm A binder resin solution uniformly dispersed in the following single or mixed solvent can be obtained by applying onto a base film, preferably a polyethylene terephthalate (PET) film, and then drying to form a light diffusion layer.

The method of applying the light diffusing composition to the base film is not particularly limited as long as it is commonly known in the art, and may be adopted according to the material and shape of the base film, for example, an air knife method, A gravure method, a reverse roll method, a spray method, or a blade method can be arbitrarily selected.

After apply | coating a light diffuser to a base film, a coating layer is formed by heating by irradiating hot air, infrared rays, far-infrared rays, etc.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to examples, and detailed description will be made with reference to the accompanying drawings in order to help understanding of the present invention.

However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

After dissolving a binder and a curing agent in a solvent with the following composition, a light diffusing agent was added and dispersed while stirring to prepare a composition having a volume resistivity of 4 × 10 ¹⁰ Ωcm. The occurrence of electrostatic spots on the surface, brightness and luminance uniformity were evaluated and the results are shown in Table 2.

Solvent 41.4 parts by weight

(n-butyl acetate, volume resistivity 2.08 × 10 ¹⁰ 10cm)

25.4 parts by weight of binder resin

(Acrydick AA-960-50, manufactured by Aekyung Chemical Co., Ltd., 55% solids)

2.9 parts by weight of curing agent

(Brunnock DN-950, manufactured by Aekyung Chemical Co., Ltd.)

30.3 parts by weight of light diffusing agent

(Tech Polymer MBX-15, manufactured by Sekisui Corporation)

Example 2

Using the same apparatus and method as in Example 1, a light diffusing composition having a volume resistivity of 2 × 10 ⁹ Ωcm was prepared with the following composition, and the occurrence of electrostatic spots on the surface of the light diffusing film, luminance and luminance uniformity were evaluated. The results are shown in Table 2 together with Example 1.

Solvent 41.4 parts by weight

(Methylethylketone: toluene = 1: 1, volume resistivity 1.06 × 10 ⁹ Ωcm)

25.4 parts by weight of binder resin

(Acrydick AA-960-50, Aekyung Chemical Co., Ltd.)

2.9 parts by weight of curing agent

(Brunnock DN-950, manufactured by Aekyung Chemical Co., Ltd.)

30.3 parts by weight of light diffusing agent

(Tech Polymer MBX-15, manufactured by Sekisui Corporation)

Comparative Example 1

Using the same apparatus and method as in Example 1, a light diffusion composition having a volume resistivity of 6 × 10 ¹² μm cm was prepared using the following composition, and the electrostatic spot occurrence, brightness and brightness uniformity of the surface of the light diffusion film were evaluated. The results are shown in Table 2 together with Example 1.

Solvent 41.4 parts by weight

(Toluene, volume resistivity 1.29 × 10 ¹³ cm)

25.4 parts by weight of binder resin

(Acrydick AA-960-50, Aekyung Chemical Co., Ltd.)

2.9 parts by weight of curing agent

(Brunnock DN-950, manufactured by Aekyung Chemical Co., Ltd.)

30.3 parts by weight of light diffusing agent

(Tech Polymer MBX-15, manufactured by Sekisui Corporation)

Comparative Example 2

Using the same apparatus and method as in Example 1, a light diffusing composition having a volume resistivity of 7.1 × 10 ¹³ μm cm was prepared using the following composition, and the occurrence of electrostatic spots on the surface of the light diffusing film, luminance and luminance uniformity were evaluated. The results are shown in Table 2 together with Example 1.

Solvent 41.4 parts by weight

(Toluene: xylene = 1: 1, volume resistivity 2.08 × 10 ¹³ cm)

25.4 parts by weight of binder resin

(Acridic DU-589, manufactured by Aekyung Chemical, 55% solids)

2.9 parts by weight of curing agent

(Brunnock DN-950, manufactured by Aekyung Chemical Co., Ltd.)

30.3 parts by weight of light diffusing agent

(Tech Polymer MBX-15, manufactured by Sekisui Corporation)

Experimental Example: Preparation of Light Diffusion Film

Using a gravure coating machine, the light diffusing composition prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was dried on a 100 μm thick polyethylene terephthalate film (SH71S) of 20 m / min so as to have a dry coating amount of 14 g / m 2. It was applied at a speed and dried at 100 ℃ to prepare a light diffusing film.

TABLE 2

<Assessment Methods>

-Volume resistivity

Using a megohmmeter (model name DSM 8103) manufactured by Dong-A Radio Wave Co., Ltd., the volume resistance was measured at a room temperature of 1.9 cm between electrodes.

-Electrostatic spot

The coated surface of the light diffusion film after drying was visually observed to evaluate the presence of coating defects in the shape of a bird or an oval.

Average luminance and luminance uniformity

The light-diffusion film was ringed on the light guide plate of the LCD backlight unit and measured using TOPCON's luminance meter BM-7. The highest luminance value for the luminance value at any ten points was L _max and the lowest. When the luminance value is L _min , the luminance uniformity was calculated according to Equation 1 below, and it was determined that the luminance uniformity was good when the luminance uniformity was 70% or more.

As can be seen from the results of the present invention, in the case of the light-diffusion composition (Examples 1 to 2) in which the volume resistivity of the organic solvent is adjusted so that the volume resistivity of the light-diffusion film composition is 1 × 10 ¹³ Ωcm or less according to the present invention. It was confirmed that the electrostatic spots do not occur, and the luminance and the luminance uniformity were excellent.

On the other hand, in Comparative Examples 1 to 2 in which the volume resistivity of the light diffusion film composition exceeds 1 × 10 ¹³ Ωcm, electrostatic spots are generated, luminance characteristics are deteriorated, and luminance uniformity is also poor, which is suitable for applying to various image display devices. Did not do it.

According to the present invention, the composition of the light-diffusion film in which the volume resistivity of the organic solvent used so that the volume resistivity of the composition for the light-diffusion film is 1 × 10 ¹³ Ωcm or less does not generate an electrostatic spot, resulting in a clean appearance and luminance characteristics. It has excellent brightness uniformity and is suitable for application to various image display devices, in particular, backlights or LED lamps for LCDs.

Although the present invention has been described with reference to one embodiment, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Claims (11)

100 parts by weight of binder resin; A homopolymer obtained by using an inorganic light diffusing agent selected from silica, zirconia, calcium carbonate, barium sulfate and titanium oxide, and one or two or more monomers selected from propylene, acrylonitrile, methyl (meth) acrylate and urethane, or 10 to 500 parts by weight of a light diffusing agent selected from organic light diffusing agents which are copolymers of these monomers; And 30 to 500 parts by weight of an organic solvent having a volume resistivity of 5 × 10 ¹² Ωcm or less, and a volume resistivity of 1 × 10 ¹³ Ωcm or less. delete The method of claim 1, wherein the organic solvent is toluene, dichloro ethane, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, ethyl acetate, n-butyl acetate, xylene, cyclohexane, tetrahydrofuran, n- At least one selected from the group consisting of heptane and cellulsolve acetate, wherein the volume resistivity is 5 × 10 ¹² cm 3 or less. The method of claim 1, wherein the binder resin is selected from the group consisting of polyvinyl alcohol, ethylene vinyl copolymer, acrylic resin, polyester resin, styrene resin, alkyd resin, amino resin, polyurethane resin, and epoxy resin. At least one selected. delete delete delete The composition according to claim 1, further comprising 0.1 to 10 parts by weight of a curing agent, an antistatic agent, a leveling agent or a humectant, respectively, based on 100 parts by weight of the binder resin. The light-diffusion film obtained by apply | coating the composition for light-diffusion films of any one of Claims 1, 3, 4, and 8. The backlight for LCD which employ | adopted the light-diffusion film of Claim 9. The LED lamp which employ | adopted the light-diffusion film of Claim 9.