KR101581737B1 - Light diffusion structure - Google Patents

Abstract

An object of the present invention is to provide a light diffusing structure having a high hiding power and a high diffusing intensity when used in combination with a light source, which is difficult to charge, and has high solvent resistance at low cost.

D₇₅/D₂₅

1.4 를 만족하는 것을 특징으로 하는 광확산 구조체이다.The present invention provides a light diffusion structure having a base layer and a light diffusion layer laminated thereon, wherein the light diffusion layer contains a resin and an inorganic particle, the shape of the inorganic particle is a pebble shape, a columnar plate shape, The particle size distribution sharpness (D ₇₅ / D ₂₅ ) is 1.0

D ₇₅ / D ₂₅

1.4. ≪ / RTI >

The light diffusion structure

Description

[0001] LIGHT DIFFUSION STRUCTURE [0002]

The present invention relates to a light diffusion structure having a light diffusion layer excellent in acid resistance and organic solvent resistance. More particularly, the present invention relates to a light diffusion structure that can be preferably used for a backlight unit of a liquid crystal display device, a lighting device, a screen of a projector, and the like.

The light diffusion structure is used for the purpose of diffusing the light of a source of light such as a point light source such as a bulb or an LED or a light source such as a fluorescent tube to obtain a uniform flat light with a high frontal luminance. This light diffusing structure can be used as a light diffusing film for a backlight unit of a liquid crystal display such as a cellular phone, a digital camera, and a liquid crystal television, a screen for a liquid crystal projector, a light diffusing plate for household lighting equipment and facility lighting, And is widely used as a POP for promotional use and a light diffusion film for various illuminations.

The light diffusion structure is known to have a structure in which a light diffusion layer composed of a transparent synthetic resin (binder) layer formed by dispersing spherical transparent particles such as silica, acrylic or polystyrene as a light diffusion material is formed on the surface of a transparent substrate .

With respect to the light diffusion structure, there is a demand for a function of deleting the dot pattern, the linear pattern, the outline of the illumination light source, and the bright spots of the light guide plate by the hiding power based on the light diffusion action to give uniform surface light emission.

Therefore, the light diffusion structure is required to have a large haze measured based on JIS K 7105. Further, the light diffusion structure is also required to have a function of converging the divergent light from the light source to maintain high brightness. This function is usually measured by a goniometer and the like, the light source is arranged on the back side of the light diffusion structure, the light receiver is scanned in the range of 0 to 180 DEG on the front side, and the transmission light amount is plotted with respect to the angle. The condensing ability of the light diffusion structure is evaluated based on whether the transmitted light is concentrated in a narrow direction.

However, conventionally, since the spherical silicon particles are used as the light diffusing material, the total light transmittance is high, but the haze is small and the light diffusibility can not be ensured. Further, since the spherical particles have strong retroreflectivity of light, the light collecting ability is insufficient. In addition, when the spherical particles are used as the light diffusing material, there is a case where light is strongly scattered or reflected in a specific direction, which may cause problems such as flashing and uneven brightness. In addition, the spherical silicon was very expensive.

Generally, since the light diffusion structure is disposed on the front surface of the light source, if the resin fine particles are used, the surface of the light diffusion layer is likely to be charged, and as a result, it is easy to adsorb foreign matter. When an organic solvent is used in the step of removing adhering foreign substances, cracks are not generated in the resin fine particles, and the luminance is lowered, which causes a decrease in production efficiency.

In addition, the light diffusion structure often flows in the form of a roll, and if foreign matter is adhered to the light diffusion structure, the surface of the light diffusion layer tends to be scratched.

In addition, when the expensive and low-cost resin particles are used as the fine silica particles, the light diffusing surface is scratched and the resin particles are removed in the film processing step, the Thomson mold, and the assembling step of the backlight unit The problem was likely to occur.

In paragraph 0048 of Patent Document 1, the use of deformed particles such as a plate shape, an ellipsoid shape, a main shape, a polygonal shape, a disc shape, a star shape, a surface wrinkle shape, , And it is disclosed that a small amount of the additive has an excellent light diffusibility and a high total light transmittance and brightness.

(Patent Document 1) Japanese Laid-Open Patent Publication No. 2007-133173

However, according to the knowledge of the inventors of the present invention, even when using a deformed particle such as a plate or disc as the light diffusing material, the light diffusion effect and high total light transmittance described in Patent Document 1 can not be obtained when the deviation of the particle diameter is large .

An object of the present invention is to provide a light diffusing structure having a high hiding power, a diffused light of high luminance when used in combination with a light source, and a high solvent resistance.

The present inventors have found that a light diffusion structure having a high total organic light transmittance and haze, a high hiding power, a high frontal luminance and a high organic solvent can be obtained by using inorganic particles having a sharp particle size distribution and a specific shape as a light diffusion material .

That is,

1. A light diffusion structure having a substrate and a light diffusion layer laminated thereon, wherein the light diffusion layer contains a resin and inorganic particles,

D₇₅/D₂₅

1.4 를 만족하는 것을 특징으로 하는 광확산 구조체,The shape of the inorganic particles is in the form of a pebble shape, a columnar plate shape, or a hexagonal columnar shape, and its particle size distribution sharpness (D ₇₅ / D ₂₅ ) is 1.0

D ₇₅ / D ₂₅

1.4. ≪ / RTI >

<θ_t>

15°를 만족하는 전항 1 에 기재된 광확산 구조체,2. Average slope of inorganic particles in the light-diffusing layer &_lt;

<? _t >

15. The light diffusion structure according to claim 1,

3. The light diffusion structure according to item 1 or 2, wherein the inorganic particles are porous or hollow,

4. The light diffusion structure according to any one of items 1 to 3 above, wherein the inorganic particles are aluminum salt hydroxide particles represented by the following formula (1)

_{M a [Al 1-x M} 'x] b A z B y (OH) n · mH 2 O (1)

a

1.35, 2.7

b

3.3, 0

m

5, 4

n

7, 0

x

0.6, 1.7

y

2.4, 0

z

0.5 이다)M is at least one cation selected from the group consisting of Na ⁺ , K ⁺ , NH ⁴⁺ , H ₃ O ⁺ and Ca ²⁺ , M 'is at least one cation selected from the group consisting of Zn ²⁺ , Cu ²⁺ , Ni ^{2 +} , Sn ⁴⁺ , Zr ⁴⁺ and Ti ⁴⁺ , A is at least one organic acid ion, B is at least one inorganic acid ion, and a, b, m, n, x, y and z are 0.7

a

1.35, 2.7

b

3.3, 0

m

5, 4

n

7, 0

x

0.6, 1.7

y

2.4, 0

z

0.5)

5. The light diffusion structure according to any one of items 1 to 4, wherein the resin is an acrylic resin,

6. The light diffusion structure according to any one of items 1 to 5, wherein the total light transmittance based on JIS K 7136 of the substrate is 80 to 100% and the haze is 0 to 5%.

The light diffusion structure of the present invention has excellent total light transmittance and haze. Further, the light diffusion structure of the present invention can collect diffused transmitted light on the front face. Further, the light diffusion structure of the present invention is excellent in solvent resistance, and cracks are not generated in the inorganic particles even by the organic solvent, and the luminance is not lowered, and therefore, productivity is excellent. The light diffusion structure of the present invention has excellent hiding power. In the light diffusion structure of the present invention, the inorganic particles are hardly dropped even in each manufacturing process of film processing, Thompson-type film punching, and backlight unit assembly.

In addition, since the light diffusion structure is difficult to be charged, it is difficult for foreign substances to adhere, and cracks are not generated in the inorganic particles by the organic solvent used in the process for removing adhered foreign substances, and the luminance is not lowered. great.

Further, the light diffusion structure of the present invention does not use expensive silica fine particles and is therefore excellent in economy.

The light diffusion structure of the present invention can be used for diffusing parallel light, converging diverging light, and concealing a light source or a light emission pattern. Specifically, it is suitable for obtaining illumination with high luminance uniformity and high frontal luminance.

(Inorganic particles)

The inorganic particles used in the present invention are characterized by being in the form of a pebble-like, cylindrical, or hexagonal columnar shape.

One of the scales for specifying the shape of the particles is the Wadell circularity and sphericity which have been conventionally used in the powder industry. Wadell's sphericity s is defined by the following equation. The closer to 1, the closer to Jingu.

s = (surface area of a sphere having an equal volume with the particle) / (surface area of the particle)

Also, the circularity c of Wadell is defined by the following equation. The closer c is to 1, the closer to the origin.

c = (the projected area of the particle and the peripheral length of the area circle) / (the peripheral length of the projection plane of the particle)

c

1 로서, 단면인 타원의 (단경/장경) 의 비율 a 가 0.05

a

0.5 인 것이 바람직하다.In the present invention, the shape of the particles in the shape of a staggered (or disc-shaped) shape is a shape of a rotating ellipse having a short axis as a rotation axis as shown in an SEM photographic image of Fig. Specifically, with respect to the projected image of the particle viewed from the direction of the rotation axis, Wadell's circularity c was 0.95

c

1, the ratio a of the cross section ellipse (short diameter / long diameter) is 0.05

a

0.5.

c < 0.95 인 육각형으로서, 두께 / (정육각형의 대각선 길이) 의 비율 b 가 0.05

b

0.6 인 것이 바람직하다.In the present invention, the shape of the hexagonal columnar plate in the present invention is a square hexagonal prism shape as in the SEM photographic image of Fig. 5, with respect to the projected image of the grain viewed from the top or bottom direction, 0.88

c < 0.95, and the ratio b / b of the thickness / (diagonal length of the regular hexagon) is 0.05

b

0.6.

c

1 인 원형으로서, 두께 / (원의 직경) 의 비율 d 가 0.05

d

0.6 인 것이 바람직하다.In the present invention, the shape of the cylindrical plate is a cylindrical plate shape, as shown in the SEM photograph of Fig. 6, in the form of a flattened cylindrical shape, and with respect to the projected image of the particle viewed from the upper surface or the lower surface direction, Wadell's circularity c is 0.95

c

1, the ratio of the thickness / (diameter of circle) d is 0.05

d

0.6.

D₇₅/D₂₅

1.4 를 만족하는 것이다.Another characteristic of the inorganic particles used in the present invention is that the sharpness (D ₇₅ / D ₂₅ ) of the particle size distribution is 1.0

D ₇₅ / D ₂₅

1.4.

Here, the sharpness (D ₇₅ / D ₂₅ ) of the particle size distribution is a method of evaluating the particle size uniformity often used in the powder industry. This means that when the particle diameter on the abscissa axis and the cumulative frequency on the ordinate axis are taken as D ₂₅ and D ₇₅ , the particle diameter at which the cumulative frequency becomes 25% and the particle diameter at which the cumulative frequency becomes 25% Is defined by the value D ₇₅ / D ₂₅ .

D₇₅/D₂₅

1.4 의 범위의 값을 나타내는 것이 바람직하다. 더욱 바람직하게는 1.02

D₇₅/D₂₅

1.3 이고, 가장 바람직하게는 1.05

D₇₅/D₂₅

1.2 이다.In the present invention, the inorganic particle has a sharpness (D ₇₅ / D ₂₅ ) of the particle size distribution of 1

D ₇₅ / D ₂₅

1.4 &lt; / RTI &gt; More preferably 1.02

D ₇₅ / D ₂₅

1.3, and most preferably 1.05

D ₇₅ / D ₂₅

1.2.

Other methods of evaluating the uniformity of the particle diameter can be evaluated by the half width, the standard deviation and the coefficient of variation, and these evaluation methods have correlation with each other, and D ₇₅ / D ₂₅ , half width and standard deviation, .

The present inventors considered the relationship between the sharpness of the particle size distribution, the light diffusion effect, and the total light transmittance as follows. When the sharpness of the particle size distribution is within the above range, the particles are uniformly dispersed in the light-diffusing layer and each particle is oriented in a certain direction, that is, the plate-like particle is parallel to the upper or lower surface of the light- The total light transmittance is obtained. On the other hand, in the case where the sharpness of the particle size distribution is out of the above-mentioned range, even if the particle shape is a pebble shape, a columnar plate shape, or a hexagonal columnar shape, the particles are not uniformly dispersed in the diffusion layer, The same effect can not be obtained.

D₇₅/D₂₅

1.4 의 범위의 무기 입자로는, 예를 들어 하기 식 (1) 로 나타내는 알루미늄염 수산화물 입자를 예시할 수 있다.(D ₇₅ / D ₂₅ ) of the particle size distribution is in the range of 1

D ₇₅ / D ₂₅

As the inorganic particles in the range of 1.4, for example, aluminum hydroxide hydroxide particles represented by the following formula (1) can be exemplified.

M _a [Al _{1 - x} M ' _x ] _{b z} B _y (OH) _n揃 mH ₂ O (1)

a

1.35, 2.7

b

3.3, 0

m

5, 4

n

7, 0

x

0.6, 1.7

y

2.4, 0

z

0.5 이다)Wherein M is a cation containing at least one species selected from the group consisting of Na ⁺ , K ⁺ , NH ⁴⁺ , H ₃ O ⁺ and Ca ²⁺ . Na ⁺ contained in the weight> it is ^{K +, NH 4 +, H} 3 O +, Ca 2 +. M 'is ^{Zn 2 +, Cu 2 +,} Ni 2 +, Sn 4 +, Zr 4 + , and Ti ^{4 +} at least one kind of metal cation selected from the group consisting of, A is at least one kind of organic acid ions, B is At least one inorganic acid ion. Wherein a, b, m, n, x, y, and z are selected from the group consisting of 0.7

a

1.35, 2.7

b

3.3, 0

m

5, 4

n

7, 0

x

0.6, 1.7

y

2.4, 0

z

0.5)

The organic acid ion represented by A in the above formula (1) is preferably at least one selected from anions based on an organic carboxylic acid or an organic oxycarboxylic acid. More preferably, it is at least one selected from an organic carboxylic acid having 1 to 15 carbon atoms or an anion based on an organic oxycarboxylic acid having 1 to 15 carbon atoms. More preferably, it is selected from an organic carboxylic acid having 2 to 10 carbon atoms and 1 to 4 carboxyl groups or an anion based on an organic oxycarboxylic acid having 2 to 10 carbon atoms and 1 to 4 oxycarboxyl groups At least one species. Most preferred is anion based on at least one selected from oxalic acid, citric acid, tartaric acid, malic acid, gallic acid, glyceric acid and lactic acid.

Specifically, the inorganic acid ion represented by B in the above formula (1) is preferably at least one selected from a sulfate ion, a nitrate ion, a phosphate ion and a silicate ion. More preferably, it is at least one selected from a sulfate ion and a nitrate ion.

In the above formula (1), M is a cation containing at least one species selected from the group consisting of Na ⁺ , K ⁺ , NH ^{4 +} , H ₃ O ⁺ and Ca ^{2 +} , and is Na ⁺ in a preferred embodiment. M 'is at least one metal cation selected from the group consisting of Zn ²⁺ , Cu ²⁺ , Ni ²⁺ , Sn ⁴⁺ , Zr ⁴⁺ and Ti ⁴⁺ .

The inorganic particles can be prepared by the method described in the brochure WO 05/085168 or WO 06/109847.

Grain-like (disk-like) particles can be produced by the method described in WO05 / 085168 pamphlet, page 21, lines 19-26. That is, when the inorganic acid ion of B in formula (1) is sulfuric acid ion, the rhizome-shaped (disc-shaped) particles are preferably a mixture of aluminum sulfate and M 'sulfate, M sulfate and organic acid, And / or an organic acid salt such as oxalic acid (H ₂ C ₂ O ₄ ) in an aqueous solution of an alkali hydroxide containing the M, and heating the mixture. Specifically, it is described in the publication No. WO05 / 085168 pamphlet on page 18 Example 1-B, page 19 Example 1-G, page 20 Example 1-H and page 21 Example 1-T &Lt; / RTI &gt;

According to Example 1-B of the same brochure, 0.2 mol of aluminum sulfate and 0.2 mol of sodium sulfate are dissolved in 600 ml of pure water, and 0.015 mol of oxalic acid is added. Then, while stirring, 0.8 mol of sodium hydroxide was added to the mixed solution, and hydrothermal treatment was performed at 170 캜 for 8 hours. The cooled solution was filtered, washed with water and dried at 95 ° C for 15 hours to synthesize Na _1.02 Al ₃ (SO ₄ ) _2.03 (C ₂ O ₄ ) _0.06 (OH) _5.84 · 0.2H ₂ O have.

Hex column plate-like particles can be produced by the method described in Example 1-F on page 19 of WO05 / 085168 pamphlet. According to Example 1-F of this brochure, 0.2 mol of aluminum sulfate and 0.2 mol of sodium sulfate are dissolved in 600 mL of pure water, and 0.025 mol of oxalic acid is added. Next, while stirring, 180 ml (0.9 mol) of an aqueous solution of sodium hydroxide was added to the mixed solution, stirred for 30 minutes at room temperature, and then hydrothermally treated at 180 ° C for 20 hours. The cooled solution was filtered, washed with water and dried at 95 ° C for 15 hours to synthesize hexagonal plate-like Na _0.93 Al ₃ (SO ₄ ) _2.01 (C ₂ O ₄ ) _0.092 (OH) _5.73 · 0.2H ₂ O .

Cylindrical shaped particles can be obtained by a method described in International Publication No. 06/109847, p. 33 Example 1-F, p. 34 Example 1-K, p. 36 Example 1-O and 1-P Can be manufactured.

For example, according to Example 1-F of the same brochure, 87 ml of 1.03 mol / l aqueous solution of aluminum sulfate and 12.78 g (0.09 mol) of sodium sulfate are placed in a 1-liter container and made into 500 ml with deionized water. While stirring with a mixer, 5.53 g of ZnO (commercially available product) powder was added, stirred for 20 minutes, and then 47 ml of a 3.385 N aqueous sodium hydroxide solution was added by pouring. After stirring for 20 minutes, the mixture is transferred to an autoclave and allowed to react at 170 ° C for 2 hours. Then, after cooling, it was collected by filtration, washed with water, followed by drying 18 hours at 105 ℃ to synthesize _{Na 1.09 (Al 2.80, Zn 0.20} ) (SO 4) 2.27 (OH) 5.35 · 1.33H 2 O indicating a cylindrical plate-like .

The inorganic particles having a checkerboard shape, a cylindrical shape, or a hexagonal columnar shape, which are exemplified above, exhibit an effect equal to or greater than that of the particles by making them hollow or porous. The inorganic particles exhibiting the hollow or porous pebble shape, cylindrical plate shape, or hexagonal columnar plate shape can be obtained, for example, as described in paragraph 0021 of Japanese Unexamined Patent Publication (Kokai) No. 2007-204293 by using an aluminum salt hydroxide particle By dropwise addition of an acid or an aqueous alkali solution, followed by heating, followed by cooling, filtration, washing with water and drying. Specifically, it can be produced by the method described in Example 1 at paragraph 0064 of the same publication.

The average secondary particle diameter of the inorganic particles used in the present invention is preferably in the range of 0.1 to 5 占 퐉, more preferably in the range of 1 to 5 占 퐉.

The content of the inorganic particles in the light diffusion layer is preferably 0.1 to 200 parts by weight, more preferably 10 to 200 parts by weight, and still more preferably 100 to 200 parts by weight, based on 100 parts by weight of the resin binder.

(Suzy)

The resin is preferably an acrylic resin, and a thermosetting or photo-curable acrylic resin may be used. Examples of the acrylic resin include polyacrylic acid and esters thereof, polymethacrylic acid and esters thereof, and the like.

(Average tilt <&thgr; _t >)

<θ_t>

15°를 만족하는 것이 바람직하다. 무기 입자의 평균 경사도 <θ_t> 는, 각 입자가 광확산층 내에 있어서 광확산층의 상면 또는 하면에 평행하게 배향되어 있는지를 나타내는 척도이다. 이것은, 판 형상 입자의 상면 또는 하면과 광확산층의 상면 또는 하면이 이루는 각도의 평균으로 나타낸다. 원반 형상 입자의 경우에는, 도 12 의 정면도의 기준면 A-A' 를 포함하는 지면에 수직인 면 (기준면이라고 한다) 과 광확산층의 상면 또는 하면이 이루는 각도로 나타낸다.In the present invention, the average inclination < [theta] _t > of the inorganic particles in the light diffusion layer is preferably 0

<? _t >

15 [deg.]. The average inclination < [theta] _t > of the inorganic particles is a measure indicating whether or not each particle is oriented parallel to the upper or lower surface of the light diffusion layer in the light diffusion layer. This is expressed as an average of the angle formed by the upper surface or lower surface of the plate-shaped particle and the upper surface or lower surface of the light diffusion layer. In the case of disc-shaped particles, the angle is defined by the angle formed by the plane (reference plane) perpendicular to the plane including the reference plane AA 'of the front view of Fig. 12 and the upper or lower surface of the light diffusion layer.

Concretely, it is a value obtained by measuring an inclination degree? _T of arbitrary 20 inorganic particles in an SEM photograph of 10,000 times including the light diffusion layer in the visual field.

<θ_t>

15°인 것이 보다 바람직하고, 가장 바람직하게는 0°

<θ_t>

12°이다. <θ_t> 가 15°를 초과하면 전광선 투과율이 저하되므로 바람직하지 않다.In order to obtain a high light diffusion effect and a total light transmittance, < [theta] _t >

<? _t >

More preferably 15 °, and most preferably 0 °

<? _t >

12 degrees. If < [theta] _t > exceeds 15 DEG, the total light transmittance is lowered.

(materials)

The base used in the present invention preferably has a total light transmittance of 80 to 100% and a haze of 0 to 5% as measured by a method based on JIS K 7136, a total light transmittance of 90 to 100% and a haze of 0 To 1%. However, a substrate having a larger haze may be used depending on the application.

Examples of the substrate that can be preferably used include glass, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyethylene, acetyl cellulose, vinyl chloride resin and the like.

In consideration of the adhesive strength between the binder and the film, it is preferable that the surface of the substrate is subjected to corona treatment or other hydrophilization treatment.

The thickness of the substrate is preferably in the range of 10 to 2,000 mu m. And more preferably in the range of 30 to 1000 占 퐉. If it is thinner than 10 탆, handling becomes very difficult. If it is thicker than 2000 탆, rigidity is large, and interference stripes or shadows arising from time-course deformation due to moisture absorption and temperature changes easily occur.

(Production of light diffusion structure)

The light diffusing structure of the present invention is obtained by laminating a light diffusing agent in which inorganic particles are dispersed in a resin binder, as at least a surface (front surface) of a substrate as a light diffusion layer. The surface (surface) referred to herein is the surface of the substrate opposite to the light source. In addition to the surface (front side), the haze can be increased by laminating the light diffusion layer on the back side of the base material. The light diffusing agent preferably contains a solvent.

The light-diffusing agent is preferably prepared by blending 0.1 to 200 parts by weight of inorganic particles with respect to 100 parts by weight of the resin binder. A more preferable blending amount is 10-200 parts by weight, and a most preferable blending amount is 100-200 parts by weight.

However, when the light diffusion layer is laminated only on the surface (front side), the preferable amount of the inorganic particles is 100-200 parts by weight. As is apparent from Fig. 1, when the blending amount of the inorganic particles exceeds 200 parts by weight, the total light transmittance becomes less than 75% or the haze becomes less than 80%. On the other hand, if the blending amount of the inorganic particles is less than 100 parts by weight, the hiding ability is deteriorated.

When a thermosetting or photo-curable acrylic resin is used as the resin binder, it can be produced by curing the binder with light or heat after application. It is preferable that the light diffusing agent is defoamed before application.

The lamination of the light-diffusing layer on a substrate can be carried out by a known coating method such as brush coating, roller coating, blow coating, airless spray, roll coating, dip coating, electrodeposition coating, electrostatic coating, Conventionally known coats or printing methods such as knife coats, kiss coats, spray coats, wheeler coats or gravure printing, gravure offset printing, flat plate offset printing, die lithography, relief printing, engraving, silk screen printing, electrostatic printing, As shown in FIG.

In order to obtain the effect of orienting each of the above-mentioned particles in a certain direction, coating with a gravure coat, an air knife coat and a kiss coat is preferred.

The coating thickness of the light diffusing agent is preferably in the range of 1 to 50 mu m. If it is less than 1 mu m, the haze decreases, and when it exceeds 50 mu m, the total light transmittance decreases, which is not preferable. When the coating amount is insufficient by the coating method, there is a case where overlap printing is carried out about two to three coats.

In order to cure or stabilize the light-diffusing layer, the light-diffusing structure may be cured at room temperature or at a temperature of about 30 to 60 DEG C for about 1 to 2 weeks.

If necessary, a layer having at least one of a sticking prevention function, an antistatic function, a scratch prevention function, a second light diffusion layer function, an antireflection function and the like may be laminated on one side or both sides of the substrate.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. Various properties of the present invention were measured by the following methods. Each measurement was performed at room temperature (20 to 30 ° C) and under normal humidity (60% RH or less).

1. Measurement methods, devices and evaluation methods

(1) Measurement of transmitted light

Device: Goniometer GP-200 (Murakami Color Research Institute, Inc.)

Method: A light source is placed on the back side of the light diffusion structure, and the light receiving unit is scanned in the range of 0 to 180 degrees on the front side, and the amount of transmitted light is measured every 0.1 degree. However, with regard to the light diffusion structure, the angle when the light source and the light receiver come to the symmetric position is set to 90 degrees. During measurement, the sensitivity of the photomultiplier tube is adjusted so that the intensity of the transmitted light is at most 85 or less.

(2) The thickness of the light diffusion structure

The thickness of the light diffusion structure was measured using a specimen thickness gauge SDA-25 (Kobunshi Instrument Co., Ltd.).

(3) Measurement of average secondary particle size

Apparatus: Particle size distribution Microtrack MT3300 (Leed & Nortrup Instruments Company)

Method: 700 mg of sample powder is added to 70 ml of 0.2 wt% sodium hexametaphosphate solution, dispersed for 3 minutes by ultrasonic, and the particle size distribution is measured while stirring with a stirrer.

(4) Observation of particle shape

SEM photographs.

Device: Scanning electron microscope S-3000N (Hitachi)

Method: Acceleration voltage 15 ㎸, operating distance 10 ㎜, magnification 2 thousand times, 10,000 times, 20 thousand times

(5) Measurement of refractive index

Apparatus: Abbe refractometer 1T (ATAGO)

Method: 5 mg of sample powder was added to 5 ml of a suitable organic solvent, and the mixture was dispersed by ultrasonic wave for 10 minutes. The refractive index was determined by spreading a transparent portion on the main prism surface in a thin film form.

(6) Analysis of X-ray diffraction

Apparatus: RINT2200VX ray diffraction system (manufactured by Rigaku Denki Co., Ltd.)

, 각도 (2θ) : 5∼65°, 단계 : 0.02°, 스캔 스피드 : 4°/분, 관 전압 : 40 ㎸, 관 전류 : 20 ㎷.Method: CU-K

, Angle (2?): 5 to 65 °, step: 0.02 °, scan speed: 4 ° / min, tube voltage: 40 kV, tube current: 20 ㎷.

(7) Measurement of total light transmittance and haze

Device: Automatic Haze meter TC-H3DP (Tokyo full color)

Method: Based on JIS-K 7136 (ISO14782).

(8) Average slope <? _T >

In a SEM photograph of 10,000 times including the light diffusing layer in the visual field, the inclination of the upper or lower surface of the particle and the upper or lower surface of the light diffusing layer was measured and averaged for arbitrary 20 inorganic particles.

<Preparation of inorganic particles>

The inorganic particles were synthesized by the method described below, or commercially available inorganic particles were used.

Synthesis Example 1: Preparation of inorganic particles A

160 mol of aluminum sulfate and 0.2 mol of sodium sulfate were dissolved in 700 L of ion-exchanged water, 0.1 mol of oxalic acid (H ₂ C ₂ O ₄ ) was added thereto, and the mixture was stirred in a reaction vessel of 1 m 3. Further, 633 mol of sodium hydroxide was added to the mixed solution while stirring at a rotation speed of 89 rpm of a stirring wing, and the mixture was hydrothermally treated at 170 캜 for 3 hours. The cooled reaction solution was filtered, washed with water, and then dried and pulverized at 120 ° C for 24 hours. As a result, disk-shaped aluminum hydroxide particles (inorganic particle A) shown in the SEM photograph of FIG. 4 were obtained. Table 1 shows all the characteristics of the inorganic particle A.

Synthesis Example 2: Preparation of inorganic particles B

An inorganic particle B was obtained in the same manner as in Synthesis Example 1 except that the amount of ion-exchanged water was 1000 L and the rotation speed of the stirring blade was 76 rpm. Table 1 shows all the characteristics of the inorganic particles B.

Synthesis Example 3: Preparation of inorganic particles C

An inorganic particle C was obtained in the same manner as in Synthesis Example 1, except that the amount of ion-exchanged water was 1000 L and the rotation speed of the stirring blade was 49 rpm. Table 1 shows all the characteristics of the inorganic particles C.

Synthesis Example 4: Preparation of inorganic particles D, H and E

In addition, based on the method described in Examples 1-F and 1-A of the pamphlet of International Publication No. 05/085168 and in Examples 1-F of WO 00/109847 pamphlet, And inorganic particles D, H and E in the form of a cylindrical plate were synthesized. Of these, inorganic particles H were used as a comparative example. An SEM photograph of the inorganic particle D is shown in Fig. An SEM photograph of the inorganic particle E is shown in Fig. An SEM photograph of the inorganic particle H is shown in Fig. Table 1 shows all the characteristics of each inorganic particle.

Synthesis Example 5: Synthesis of inorganic particles F

On the basis of the method described in Example 1 of paragraph 0064 of Japanese Patent Application Laid-Open No. 2007-204293, inorganic particles A were used as &quot; blank A &quot; The obtained particles were porous hollow particles having a BET specific surface area of 102 m 2 / g and a total pore volume of 0.244 ml / g. Table 1 shows all the characteristics of the inorganic particles F.

(Inorganic particles G, I, J, and K of commercially available products)

In addition, as comparative examples, inorganic particles I (silicone powder: KMP-701 / Shin-Etsu Kagaku Kogyo Co., Ltd.) and inorganic particles J (silicone powder: calcium carbonate / : KSP-300 / Shin-Etsu Chemical Co., Ltd.) and inorganic particles K (methyl silicone powder MSP-1500M / Nikkori K.K.) were used. The properties of each inorganic particle are shown in Table 2. An SEM photograph of the diffusible fine particles G is shown in Fig. An SEM photograph of the diffusible fine particles I is shown in Fig.

Preparation example

20 g of an acrylic resin (trade name: SumiPEX MGSS / Sumitomo Chemical Co., Ltd.) was added to a mixed solvent of toluene 50 ml, 2-butanone 20 ml and butyl acetate 20 ml, and stirred at room temperature for one day to obtain a polymethacrylic acid solution Lt; / RTI &gt; Inorganic particles A to K were added to polymethacrylic acid solution to polymethacrylic acid to prepare a light diffusing agent.

Examples 1 to 10 and Comparative Examples 1 to 5

(Production of light diffusion structure)

A biaxially stretched polyester film (trade name: DIAFOLE T680E / Mitsubishi Chemical Polyester Film Co., Ltd.) having a size of 70 mm x 70 mm x t 100 m was placed on a base plate, and each light diffusing agent obtained in the preparation example was immersed in 1 Ml, applied with an applicator YBA-4 (manufactured by Yoshimitsu), and dried at 105 ° C for 2 hours to prepare a light diffusion structure. At this time, the thickness of the diffusion layer after drying was set to be 5 占 퐉 or 25 占 퐉 (after drying, the thickness becomes about 1/5 of that at the time of coating). The thickness of the diffusion layer was calculated on the basis of the thickness of the test piece by measuring the thickness of the test piece with a thickness meter of the test piece after drying, and it was confirmed that the thickness was 5 占 퐉 or 25 占 퐉. Table 3 shows the production conditions of the light diffusion structure.

(Characteristics of light diffusion structure)

The prepared test pieces were set on an automatic haze meter, and the total light transmittance and the scatter transmittance were measured by measurement based on JIS K 7136 to calculate the haze. Table 3 shows all the characteristics of each of these film test specimens. Next, a light source was disposed on the back side of the light diffusion structure, and the amount of transmitted light was measured using a goniophotometer. The results are shown in Fig. 2 and Fig.

Table 3 shows the light diffusion structure No. 3. As shown in the evaluation results 1 to 10, the light diffusion structure of the present invention has a total light transmittance of 75% or more and a haze value of 60% or more when the diffusion layer thickness is in the range of 5 to 25 m.

On the other hand, in the light diffusion structure No. 1 coated with spherical aluminum salt hydroxide particles. 12 has a large total light transmittance but a small haze, which is not suitable for a light diffusion structure.

The light diffusion structure No. 2 coated with the spherical silicon powder. 13 and 15 all have a total light transmittance of 70% or more and a haze of 80% or more.

Light diffusion structure No. 1 6 and No. 14, when the thickness of the diffusion layer is increased to 25 占 퐉, the light diffusion structure No. of the present invention can be obtained. 6, the haze was increased to 95% or more. 14, the haze was as high as 82%, and the total light transmittance was reduced to less than 75%.

2, which shows the amount of transmitted light measured using a goniophotometer, the light diffusion structure No. 1 using the discotic inorganic particles of the present invention. 5 to 7 (Examples 5 to 7), the front face is set to 0 占 and the half width width is within 3 占 (the width of the angle at which the amount of transmitted light is 0.5 by setting the amount of transmitted light in the 90 占 direction to 1) It can be seen that there is an effect of collecting in front. In addition, since scattering of strong light with respect to a specific direction other than the 90 DEG direction is not observed, uniform illumination is obtained.

On the other hand, the light diffusion structure No. 1 using the spherical aluminum salt hydroxide particles. 12 (Comparative Example 2), as is clear from Fig. 2, it has a strong peak having a half width of 10 ° but anomalous in the front direction. This is a non-uniform, "flashing" light from the front.

Further, as shown in Fig. 3, the light diffusion structure No. 2 using the silicon-based powder as the inorganic particles. 13 (Comparative Example 3) and No. 3 15 (Comparative Example 5), the half-widths were 10 ° or more and 5 ° or more, respectively, and the effect of collecting transmitted light in front was smaller than that of the inorganic particles of the present invention. 14 (Comparative Example 4). 12 (Comparative Example 2).

In the light diffusion structure of the present invention, the blending amount (parts by weight) of the inorganic particles C with respect to the amount of the binder to be applied and the values of the total light transmittance, the scattering transmittance and the haze are shown in the graph of Fig. According to Fig. 1, the total amount of the inorganic particles C is increased and the total light transmittance is lowered, and conversely, the haze is increased. The light diffusion structure of the present invention maintains a total light transmittance of 80% or more even when blending at most 200 parts by weight of the inorganic particles C, but the haze value is not significantly increased even when blending at least 200 parts by weight.

If the blending amount is less than 100 parts by weight, the haze becomes less than 80%, which is not preferable.

Light diffusion structure No. 1 6 (Example 6) is shown in Fig. 10 is a cross-sectional view of the light diffusion structure No. 1; 6 is enlarged by 10000 times. However, the surface of the light-diffusing layer is photographed at an angle of 45 DEG counterclockwise with respect to the horizontal. The average inclination of 20 particles in the field of view of Fig. 10 (including vacancies in which particles were removed at the time of cutting) was 11.3 占.

The same observation was made for the light diffusion structure No. 1. 11 (Comparative Example 1) are also shown in Fig. The average slope at this time was 30 ° or more. In other words, the inorganic particles B having a particle size distribution sharpness of 1.11 are oriented in a direction nearly parallel to the upper or lower surface of the diffusion layer in the diffusion layer, but the inorganic particles G having a particle size distribution sharpness of 1.76 are not oriented in a certain direction.

(Evaluation of Concealability of Light-diffusing Structure)

The back surface facing the surface is made of an acrylic resin having an external dimension of 50 mm x 100 mm and a thickness of 1.6 mm and has a thickness thinner with distance from one side of 100 mm. A reflective film (RF188 / Tsidzden) was adhered to the back side of the wedge-shaped light guide plate subjected to roughening of the gradient pattern by hairline processing with double-sided tape, and each film test piece prepared on the surface was placed. The cold cathode tube was set on the thick side of the light guide plate, and the lamp was turned on at a tube voltage of 1200 V and a tube current of 5 mA.

Subsequently, the pattern hiding ability of the light diffusion structure was evaluated by observing whether the gradation pattern was visually observed as a stripe at a distance of 30 cm from the surface of the light guide plate. The evaluation was carried out in the following four stages. The results are shown in Table 3.

A: The pattern can not be recognized at all.

Good: The pattern can hardly be seen.

?: A little pattern can be visually confirmed.

X: The pattern can be clearly recognized.

(Solvent resistance test)

One drop of isopropyl alcohol was dropped on the surface of the light diffusion structure, and the mixture was allowed to stand at room temperature for 5 minutes to evaporate. Thereafter, isopropyl alcohol dripping was observed at a position of 30 cm from the surface of the light guide plate To evaluate the solvent resistance of the light diffusion structure. The evaluation was evaluated in the following three stages. The results are shown in Table 3.

○: Almost no signs of loading can be seen.

B: It is slightly visible that the dropping trail is dark.

X: It can clearly be seen that the drop trail is dark.

INDUSTRIAL APPLICABILITY The light diffusion structure of the present invention can be applied not only to indoor light fixtures such as backlight light diffusion layers and liquid crystal projector screens of liquid crystal panels but also to outdoor light fixtures such as interior light type road signs and POPs for promotional POP Can be widely used.

1 is a graph showing the values of total light transmittance, scattering transmittance and haze with respect to the blending amount of the inorganic particles C. Fig.

FIG. 2 is a graph showing the light diffusion structure No. 2 measured using a goniophotometer. 5, 6, 7 and 12, respectively.

FIG. 3 is a graph showing the light diffusion structure No. 3 measured using a goniophotometer. 13, 14 and 15, respectively.

4 is a SEM photograph of the inorganic particle A. Fig.

5 is a SEM photograph of the inorganic particle E. Fig.

6 is an SEM photograph of the inorganic particle D. Fig.

7 is an SEM photograph of the inorganic particles H. Fig.

8 is a SEM photograph of the inorganic particle G. Fig.

9 is a SEM photograph of the inorganic particle I. Fig.

10 is a cross-sectional view of the light diffusion structure No. 1; 6 is an SEM photograph of a 10,000-fold magnification of the light diffusion layer. However, the surface of the light-diffusing layer is photographed at an angle of 45 DEG counterclockwise with respect to the horizontal.

11 is a cross-sectional view of the light diffusion structure No. 1; 11 is enlarged 10,000 times.

Fig. 12 is a view showing a reference plane of the demon-shaped particles. Fig.

Claims (6)

A light diffusion structure comprising a substrate and a light diffusion layer laminated thereon, wherein the light diffusion layer contains a resin and inorganic particles, The shape of the inorganic particles is in the form of a pebble shape, a columnar plate shape, or a hexagonal columnar shape, and its particle size distribution sharpness (D ₇₅ / D ₂₅ ) is 1.0

D ₇₅ / D ₂₅

1.4, The particle size distribution sharp Figure (D ₇₅ / D ₂₅₎ is the particle size along the horizontal axis, when chwihaeteul the cumulative frequency on the vertical axis, the particle size is about the number of total particles, starting with a small particle size Cumulative frequencies that _25% D 25, 75% are when the particle diameter is as D _75, the light diffusion structure, characterized in that, as defined by the ratio between the D ₂₅ and D _75. The method according to claim 1, When the average inclination < [theta] _t > of the inorganic particles in the light diffusion layer is 0

<? _t >

Lt; RTI ID = 0.0 &gt; 15. &Lt; / RTI &gt; 3. The method according to claim 1 or 2, Wherein the inorganic particles are porous or hollow. 3. The method according to claim 1 or 2, Wherein the inorganic particles are aluminum salt hydroxide particles represented by the following formula (1). _{M a [Al 1-x M} 'x] b A z B y (OH) n · mH 2 O (1) M is at least one cation selected from the group consisting of Na ⁺ , K ⁺ , NH ⁴⁺ , H ₃ O ⁺ and Ca ²⁺ , M 'is at least one cation selected from the group consisting of Zn ²⁺ , Cu ²⁺ , Ni ^{2 +} , Sn ⁴⁺ , Zr ⁴⁺ and Ti ⁴⁺ , A is at least one organic acid ion, B is at least one inorganic acid ion, and a, b, m, n, x, y and z are 0.7

a

1.35, 2.7

b

3.3, 0

m

5, 4

n

7, 0

x

0.6, 1.7

y

2.4, 0

z

0.5) 3. The method according to claim 1 or 2, Wherein the resin is an acrylic resin. 3. The method according to claim 1 or 2, Wherein the total light transmittance based on JIS K 7136 of the base is 80 to 100% and the haze is 0 to 5%.

Images