KR101392288B1 - Diffusion sheet and back lighting unit using same - Google Patents

Abstract

The present invention is characterized in that a plurality of convex shapes having a major axis and a minor axis are formed on one side of a sheet, a longitudinal direction of the convex shapes is aligned in one direction, and a ray is incident on the other side of the sheet at an incident angle of 0 The outgoing light intensity distribution 1 of the light beam emitted from one side of the sheet satisfies the following conditions (1) and (2).

(1) The outgoing angle at which the intensity of 50% with respect to the outgoing intensity at the outgoing angle of 0 is 15 to 25 degrees with respect to the outgoing intensity distribution 1 in the plane perpendicular to the longitudinal direction of the convex shape.

(2) For an output intensity distribution 1 in a plane perpendicular to the sheet surface and parallel to the longitudinal direction of the convexity, an output angle at which the intensity is 50% of the output intensity at an output angle of 0 is 0.5 to 5 degrees Range.

According to the present invention, a diffusion sheet excellent in the effect of anisotropic diffusion of light and a backlight unit excellent in luminance and homogeneity are provided.

Diffusion sheet, backlight unit

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a diffusing sheet and a backlight unit using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various display devices, in particular, a diffusion sheet preferable for a backlight unit of a liquid crystal display device, and a backlight unit using the same.

Liquid crystal display devices are used for various applications such as notebook PCs, mobile phone devices, televisions, monitors, car navigation systems, and the like. A liquid crystal display device has a structure in which a backlight unit as a light source is mounted and controlled by controlling light beams from the backlight unit through liquid crystal cells. The characteristic required for this backlight unit is not only as a light source that emits light but also brightens the whole screen uniformly.

The configuration of the backlight unit can be roughly classified into two types.

One is called a sidelight type backlight. This is a method mainly used for, for example, a notebook PC in which thinning and miniaturization are required. And a light guide plate is used as a basic structure. In the case of the sidelight type backlight, a fluorescent tube is provided on the side surface of the light guide plate, a light ray is incident on the light guide plate from the side and the light is totally reflected within the light guide plate, The light is emitted from the front surface of the light guide plate to function as a backlight or a surface light source. In the case of the sidelight type backlight, in addition to these constitutions, a reflective film that functions to reflect and reuse the light leaking from the back surface of the light guide plate, a diffusion sheet that uniformizes the light emitted from the front surface of the light guide plate, and a prism sheet Various kinds of optical films have been used.

Another method is called direct-type backlight. This is a method that is preferably used for a television application in which a large size and a high brightness are required. As a basic configuration, a light pipe is not used, but a fluorescent tube is directly arranged inside the screen. A plurality of linear or partially linear fluorescent tubes are arranged in parallel on the inner side of the screen, so that it is possible to cope with a large screen, and brightness can be sufficiently secured. However, a brightness deviation (luminance deviation) in the screen due to a fluorescent tube provided inside the screen, which is also characteristic, occurs. That is, the fluorescent tubes immediately above the arranged fluorescent tubes are bright and the fluorescent tubes between adjacent fluorescent tubes are dark (tube deviation). For this reason, in the direct-type backlight, a light diffusion plate (a white board) having a very strong light-diffusing property is disposed on the fluorescent tube side in order to solve the deviation of the tube, thereby achieving uniformity of the screen (Patent Document 1). The optical diffusion plate is a light diffusion plate made of acrylic resin or polycarbonate resin in which fine particles are dispersed. The optical diffusing plate eliminates the tube deviation to make the screen uniform. However, since the light diffuses strongly, the total light transmittance is low and the light utilization efficiency is poor. Further, since the light is diffused too strongly, the light is dispersed in unnecessary directions. As a result, the brightness of the front surface becomes insufficient when necessary. Thus, a diffusing sheet exhibiting a condensing effect in the front direction is provided while diffusing light isotropically on the optical diffusing plate (Patent Document 2). This diffusion sheet is a sheet called a bead sheet in which a diffusion layer containing fine particles such as organic crosslinked particles is formed on a base sheet and is an optical film showing a directivity to some extent in a direction different from a light diffusion plate. In addition to these, a reflection film for reflecting the light emitted backward from the fluorescent tube, and a prism sheet for further enhancing the light-condensing property, if necessary, are further mounted.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-29091

Patent Document 2: JP-A-2001-324607

In the case of the direct-type backlight, it is necessary to eliminate the luminance deviation derived from the fluorescent tube on the inner side of the screen, and to make both the screen uniformity and the brightness high. Normally, as a direct-type backlight, a light diffusing plate having a very strong light diffusing property is provided as described above, and the panel deviation is eliminated by the plate-like member to improve uniformity of the screen. However, in the case of a light diffusion plate with an emphasis on uniformity, since the total light transmittance is low and the light utilization efficiency is poor, high brightness is not achieved. In the case of a light diffusing plate with an emphasis on luminance, the uniformity can not be increased because the total light transmittance is high and light diffusivity is deteriorated. In other words, the phenomenon of the rationale occurs. In addition, it is obvious that uniformity is further lowered only with a beadsheet, a prism sheet, and a brightness enhancement sheet that have conventionally been used.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a diffusion sheet excellent in the anisotropic diffusion effect of light in view of the background of the prior art. That is, according to the present invention, an efficient diffusing effect is exhibited by such a diffusion sheet, thereby effectively eliminating the tube deviation derived from the fluorescent tube, thereby achieving screen uniformity and high luminance characteristics.

The present invention adopts the following means in order to solve such a problem. That is, in the diffusion sheet of the present invention, a plurality of convex shapes having a major axis and a minor axis are formed on one side of a sheet, the longitudinal directions of the plurality of convex shapes are aligned in one direction, (1) and (2) satisfy the following conditions (1) and (2): Outgoing light intensity distribution 1 of light rays emitted from one side of the sheet when a light ray is incident at an angle of 0 °.

(1) The outgoing angle at which the intensity of 50% with respect to the outgoing intensity at the outgoing angle of 0 is 15 to 25 degrees with respect to the outgoing intensity distribution 1 in the plane perpendicular to the longitudinal direction of the convex shape.

(2) For an output intensity distribution 1 in a plane perpendicular to the sheet surface and parallel to the longitudinal direction of the convexity, an output angle at which the intensity is 50% of the output intensity at an output angle of 0 is 0.5 to 5 degrees Range.

In the diffusion sheet of the present invention, a plurality of stripe-shaped convex shapes are formed on one side of the sheet, and the longitudinal direction of the plurality of convex shapes is aligned substantially in one direction, Each of which has a shape obtained by deleting at least an area of an edge angle of not less than 80 DEG and not more than 90 DEG from the semicircular shape, and the other surface of the sheet is roughened.

In the diffusion sheet of the present invention, a plurality of stripe-shaped convex shapes are formed on one side of the sheet, and the longitudinal direction of the plurality of convex shapes is aligned substantially in one direction, Each shape in the cross section is a diffusing sheet having a shape obtained by deleting at least an edge angle of not less than 90 DEG and not more than 90 DEG from a semi-elliptical shape whose major axis direction is perpendicular to the sheet surface.

Further, the backlight unit using the diffusion sheet of the present invention includes a plurality of linear light sources in a substantially parallel arrangement, a light source in a configuration having a plurality of linear portions in a substantially parallel arrangement, and a light source And the diffusion sheet of the present invention is arranged such that the longitudinal direction of the convex shape is parallel to the direction parallel to the linear portion of the light source.

(Effects of the Invention)

According to the present invention, a diffusion sheet capable of effectively exerting an effect of anisotropic diffusion of light can be provided. By attaching the diffusion sheet to a backlight unit of a liquid crystal display device, particularly a direct-type backlight, high screen uniformity and high luminance characteristics can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing the surface shape of the diffusion sheet of the present invention. Fig.

Fig. 2 is a diagram schematically showing a preferable base structure of the diffusion sheet of the present invention. Fig.

Fig. 3 is a diagram schematically showing the surface shape of the diffusion sheet of the present invention having a stripe-like convex shape.

4 is a cross-sectional view of a stripe-shaped convex shape.

5 is a view showing a mold for forming a stripe-shaped convex shape.

(Description of reference numerals showing main parts of the drawings)

1: diffusion sheet of the present invention

2: Linear convex shape of one side (A side) of the diffusion sheet

3: substrate

4: rough surface of the other side (B side) of the diffusion sheet

5: Edge angle of the convex cross section of the stripe shape

6: a mold for forming a stripe-shaped convex shape

7: unit sectional shape of the mold 8: edge angle of the unit sectional shape

The present invention has been extensively studied on the above problem, that is, a diffusing sheet excellent in the effect of anisotropic diffusion of light. As a result, it has been found that a plurality of convex shapes having long and short axes are formed on one side (hereinafter referred to as A side) And the light diffusion behavior of the diffusion sheet is controlled by adjusting the longitudinal direction of the convex shape of the diffusion sheet to substantially one direction.

The diffusion sheet of the present invention is characterized in that a plurality of convex shapes having a major axis and a minor axis are formed on one side of the sheet, the longitudinal direction of the plurality of convex shapes is aligned in one direction, The outgoing light intensity distribution 1 of the light ray emitted from one side of the sheet satisfies the following conditions (1) and (2).

(1) The outgoing angle at which the intensity of 50% with respect to the outgoing intensity at the outgoing angle of 0 is 15 to 25 degrees with respect to the outgoing intensity distribution 1 in the plane perpendicular to the longitudinal direction of the convex shape.

(2) For an output intensity distribution 1 in a plane perpendicular to the sheet surface and parallel to the longitudinal direction of the convexity, an output angle at which the intensity is 50% of the output intensity at an output angle of 0 is 0.5 to 5 degrees Range.

The diffusion sheet of the present invention has a configuration in which a plurality of convex shapes (hereinafter referred to as line-shaped concave-convex patterns) having a major axis and a minor axis aligned in one direction in the longitudinal direction are formed on the A-plane. The term " approximately aligned in one direction " refers to a state in which the longitudinal direction of each convex shape is less than +/- 15 degrees with respect to a direction in which the longitudinal direction of each convex shape is averaged in the film plane. And the anisotropic diffusivity is expressed by the line-shaped concave-convex pattern on the A-plane. In order to solve the brightness variation according to the shape of the light source and efficiently increase the screen uniformity in the direct-type backlight in which the linear light sources are arranged in parallel in the plane, the member provided on the upper side does not diffuse the light isotropically strongly, Can be achieved by strongly diffusing in a direction perpendicular to the longitudinal direction. A diffusion sheet exhibiting strong light diffusibility in one direction, that is, anisotropic diffusivity is suitable. In the present invention, this anisotropic diffusivity is realized by a line-shaped concave-convex pattern of the surface.

Therefore, when the diffusion sheet of the present invention is attached to the backlight unit having the structure described below, the linear light source image (light source image) is diffused by the effect of the anisotropic diffusion to eliminate the brightness deviation, And a backlight unit having high uniformity and high brightness can be obtained.

The pattern formed on the A side of the diffusion sheet of the present invention is characterized by having a long axis and a short axis, and a plurality of convex shapes (line-shaped concave-convex patterns) in which the longitudinal direction, i.e., the longitudinal direction is aligned substantially in one direction. Fig. 1 illustrates the surface shape of the A-plane of the diffusion sheet of the present invention. Fig. 1 (a) and Fig. 3 (a) show the pattern in the sheet surface, and Figs. 1 (b) and 3 (b) show the sheet cross-section pattern in the cross section perpendicular to the longitudinal direction of the convex shape.

The pattern in the sheet surface of the A side of the diffusion sheet of the present invention is characterized in that each convex shape extends in one direction (line shape) as exemplified in Figs. 1 (a) and 3 (a) . Further, it is a surface laid on the front surface so that the longitudinal direction of each line-shaped convex shape is aligned in one direction. The diffusion sheet of the present invention exhibits anisotropic diffusivity in which the longitudinal direction of the line-shaped convex shape is aligned in one direction so as to be strongly diffused in the direction perpendicular to the longitudinal direction and weakly diffused in the parallel direction. In addition, it is preferable that the line-shaped convex shape is formed on the entire surface of the sheet without gaps, that is, without flattening. Therefore, the number of components of the light rays incident on the diffusion sheet is not diffused, Is improved.

The sheet cross-section pattern of the A-plane of the diffusion sheet of the present invention (a pattern that is observed on a cross section perpendicular to the longitudinal direction of the convex shape) is a curved pattern in which curves such as arcs are associated with each other. For example, A pattern in which a curved line of a semicircular shape and a semi-elliptic shape (or an inverted shape thereof) such as a lenticular lens, a pattern in which the curved lines are combined, and the like can be mentioned as preferable examples.

Regular or irregular patterns can be suitably used for the regularity of the in-sheet pattern and the sheet cross-section pattern of the A-plane of the diffusion sheet of the present invention. However, in the following points, A random pattern in which shapes different in shape and size irregularly than patterns are arranged may be preferable. In the case of a random pattern, optical interference patterns and moiré patterns between the optical sheets and the liquid crystal cell patterns other than the sheet are prevented, and defects are less noticeable when mounted on the backlight unit, thereby improving uniformity. As shown in Fig. 1 (a), the random pattern is preferably irregular in the major axis and the minor axis of the convex shape extending in one direction in the pattern in the sheet plane. Also, as shown in Fig. 1 (b), it is preferable that the shapes of the cross section of the sheet are not the same, irregular shapes are connected, and the arrangement pitch is random.

The length in the major axis direction of each convex shape forming the line-shaped pattern in the pattern in the sheet plane of the A side of the diffusion sheet of the present invention is preferably longer as the length in the minor axis direction is longer. If the length in the major axis direction is long, the anisotropic diffusion property can be improved. The ratio of the length in the major axis direction to the length in the minor axis direction (length in the major axis direction / length in the minor axis direction) of each convex shape is preferably 10 or more, and the shape in which the most anisotropic diffusivity is improved is as shown in Fig. It is a stripe shape with a very long linear shape.

In the case of an irregular pattern as shown in Figs. 1 (a) and 1 (b), for example, the pitch (that is, the length in the short axis direction of the pattern) of the sheet cross section pattern of the A side of the diffusion sheet of the present invention is 2 To 15 mu m, and the height is in the range of 0.5 to 10 mu m. Here, the pitch is the length in the thickness direction from the straight line connecting the adjoining concave portions of the pattern to the uppermost portion, and the length and height between adjacent uppermost portions of the pattern. By forming an irregular curve shape in this range, it becomes possible to satisfy the range of emission intensity distribution described later. This range is an example, and even if it is outside this range, it can be advantageously used if it satisfies the emission intensity distribution described later.

In the case of regular patterns as shown in Figs. 3 (a) and 3 (b), a shape obtained by deleting at least an edge angle of 80 to 90 degrees from the semicircular shape, or a shape in which the major axis direction is perpendicular to the sheet surface An area of at least an edge angle of 80 ° or more and 90 ° or less is deleted from the semi-elliptical shape. Will be described with reference to FIG. Fig. 4 (a) shows a semicircular shape or semi-elliptical shape which is the basis of the above shape. The shape obtained by removing the region (hatched portion in Fig. 4 (b)) of the edge angle (5 in Fig. 4 (b)) of 80 degrees or more and 90 degrees or less from the basic shape is removed from the diffusion sheet having the regular pattern of the present invention It is the shape used.

An area having a large edge angle is a region that serves to direct light rays (light rays incident from the horizontal direction with respect to the sheet surface) toward the front face at a high incident angle on the diffusion sheet, and in order to improve the front luminance of the backlight unit, Area. However, while the front luminance is improved, components emitted in the high emission angle region (region close to the horizontal direction with respect to the sheet surface) increase. As a result, an area which is bright in the front but bright in the horizontal direction with respect to the seat surface is generated, and the luminance deviation of the backlight unit is displayed. Since this tendency is particularly strong in the region where the edge angle is 80 DEG or more and 90 DEG or less, by deleting this region, a backlight unit having high uniformity can be obtained while maintaining the luminance of the front face at a high level. Preferably, by setting the edge angle to be not less than 70 DEG and less than 80 DEG, the above characteristics can be obtained in a well-balanced manner.

4 (a)), when the lengths a and b are set, the aspect ratio (b / a) is larger than 1 and smaller than 1.5 Is preferably used. Here, the length a indicates a half length (radius in the sheet surface direction) of the distance between both ends of the edge, and the length b indicates a distance from the straight line connecting between the edges to the top of the shape Respectively. When the basic shape is semicircular, the aspect ratio is 1. Here, when the aspect ratio b / a is less than 1, the effect of improving the front luminance is small, and when the aspect ratio b / a is more than 1.5, the effect of improving the front luminance is large. However, .

It is preferable that the diffusion sheet of the present invention is subjected to roughening treatment on the side opposite to the side A (hereinafter referred to as side B) of the sheet. As described above, the diffusing sheet of the present invention has a line-shaped concavo-convex pattern formed on the A side of the sheet, and the anisotropic diffusivity is developed by the pattern. However, when the diffusing sheet is mounted on the backlight unit, So that it is preferable to increase the uniformity of the backlight. It is preferable to use a line-shaped concavo-convex pattern on the outgoing surface because the effect of the anisotropic diffusion is high. Therefore, it is preferable that the B plane be a light incidence plane.

Therefore, in the diffusing sheet of the present invention, when the B-side of the sheet is roughened, light reflection on the B-plane as the light incidence plane is suppressed when mounted on the backlight unit, and light rays reflected directly from the light source and reflected / reused inside the backlight The brightness of the backlight can be increased. In addition, when used in combination with another member, adhesion with the lower member can be prevented. In addition, since slipperiness is improved by roughening treatment, it is easy to handle in various processes such as sheet cutting and backlighting depending on the shape of the backlight, as well as improvement in handling during production of the diffusion sheet, It can contribute to a reduction in defect rate.

Examples of the roughening surface to be applied to the B surface of the diffusion sheet of the present invention include those produced by coating a coating agent in which particles are dispersed in a binder resin, those prepared by transferring the shape of a mold, and those obtained by cutting and machining the surface mechanically, such as sandblasting And the like can be mentioned as preferable examples.

Any method may be preferably used. However, a method of coating a coating agent in which particles are dispersed in the binder resin can be easily and easily performed by selecting the type and combination of particles, the particle size, the amount of addition, the type of resin, It is a preferable method because it can change the degree.

Preferred examples of the particles used in this method include inorganic fine particles such as silica and organic (crosslinked) fine particles such as acrylic resin, organic silicone resin and polystyrene resin. Particle diameters of 80 nm to 50 m Is preferably used. One kind of particles may be used alone, or two or more kinds of particles may be used in combination. Examples of the binder resin include thermoplastic resins such as acrylic resin, polyester resin, polyolefin resin and polyurethane resin, thermosetting resin, and photo-curable resin.

As a preferable combination of the particles and the binder resin, it is preferable that the both are copper materials or the refractive indexes are substantially equal so that unnecessary light scattering does not occur at the interface between the particle-binder resin. It is also preferable that the thickness of the binder resin after coating is thinner than the particle diameter in order to facilitate imparting slipperiness. By making the thickness smaller than the particle diameter, the particles can escape from the resin layer after coating and function as protrusions, so that slipperiness can be easily provided.

When the degree of gloss of the B surface of the diffusion sheet of the present invention is measured using, for example, the degree of gloss, an example is shown. When a degree of gloss of 60 degrees is measured, for example, 70 to 90 in the vertical direction, and 90 to 120 in the parallel direction, and a rough surface having a glossiness within this range is preferable. Here, the 60 degree gloss is a value defined by the reflection of light incident on the sheet surface, and is a value measured based on the method defined in JIS Z8741.

(A), a line-like concavo-convex pattern is formed on one side of the base material and a roughening treatment is applied to the other side of the base material (Fig. 2 (a) (Fig. 2 (b)) in which a line-shaped concavo-convex pattern is formed on one side of the substrate and a layer in which a roughening treatment is applied to the other side of the substrate is laminated, A two-layer structure (Fig. 2 (c)) in which a pattern-formed layer is laminated and another surface of the substrate is subjected to a roughening treatment, and a layer in which a line- And a three-layer structure (Fig. 2 (d)) in which a layer subjected to roughening treatment is laminated on the other side of the substrate is preferably used.

The base material constituting the diffusion sheet of the present invention is preferably a base material which is substantially transparent or a laminate comprising at least a layer containing particles therein, or a single layer containing particles therein. In this case, when the wavelength is substantially transparent to the user, that is, when it is used in a liquid crystal display device, no absorption peak at a specific wavelength is found in a visible light region of 380 to 800 nm, To about 20%).

When a transparent substrate is used as the base material of the diffusion sheet of the present invention, the utilization efficiency of light is high because it does not contain a component for backscattering light rays inside, and consequently contributes to luminance improvement. Therefore, it is effective to use a transparent substrate when giving priority to the brightness of the backlight. In addition, when a diffusing substrate (for example, a diffusing plate or the like) is inserted between the diffusing sheet of the present invention and the light source as a backlight structure, uniformity can be ensured by combination with the diffusing plate, It is preferable not to impart diffusibility to the base material of the transparent substrate, and to make the diffusion sheet by using the transparent base material with priority given to the brightness.

Examples of the material of the transparent substrate include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymerized polyester resin, isophthalic acid copolymerized polyester resin, Polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and alicyclic olefin copolymer resins; acrylic resins such as polymethyl methacrylate; polyesters such as poly A thermoplastic resin such as a carbonate, a polystyrene, a polyamide, a polyether, a polyester amide, a polyether ester, a polyvinyl chloride, a copolymer composed of these, and a mixture of these resins. Of these, in view of mechanical strength, heat resistance and dimensional stability, a polyester resin such as a copolymer or a mixture with biaxially stretched polyethylene terephthalate, polyethylene-2,6-naphthalate or other components based thereon Is more preferably used.

Further, in the case of using a diffusible base material composed of a laminate containing a particle as a base material or a laminate material having at least a layer containing a particle therein, the uniformity of the backlight can be further increased, and as a constitution of a backlight Since uniformity can be sufficiently ensured without inserting a diffusing substrate such as a diffusion plate between the diffusion sheet of the present invention and the light source, it is effective when the uniformity is given priority.

Examples of the particles to be dispersed in the diffusible base material include inorganic fine particles such as barium sulfate, titanium oxide, magnesium sulfate, magnesium carbonate, calcium carbonate and silica; or inorganic particles such as acrylic resin, organic silicone resin, polystyrene resin, urea resin, formaldehyde condensation Organic (crosslinked) fine particles such as water and fluororesin, polyolefin resins represented by polymethylpentene, polypropylene, polyethylene, alicyclic olefin and the like dispersed in an island shape, polyethylene terephthalate, polyethylene-2,6-naphthalate (Including various kinds of copolymers) made of an acrylic resin typified by polymethyl methacrylate, etc., hollow particles, or air bubbles. The particles may be used singly or in combination of two or more. These are examples that are preferable as the diffusion element used in the diffusion sheet of the present invention and can be suitably used at least in a visible light region (380 to 780 nm) without limitation to a material having a refractive index different from that of the matrix resin.

The particle diameter of the diffusible base particles is preferably 0.5 to 50 占 퐉, more preferably 0.5 to 30 占 퐉, and most preferably 0.5 to 20 占 퐉. If the average primary particle diameter is 0.5 mu m or more, the light diffusion function as a diffusion element is sufficiently obtained in the visible light region of 380 to 780 nm. When the average primary particle diameter is 50 탆 or less, the film thickness of the base material for obtaining an effective light diffusion action is not excessively increased and the film can be made thin, which is preferable.

In addition, the shape of the particles is not particularly limited, and spherical (including true spherical shape), spheroid, rod, needle, flat, amorphous, etc. can be preferably used. In the present invention, the particle size in the shape other than the sphericity shape may be such that the length of the portion having the narrowest width satisfies the above range of 0.5 to 50 탆. Here, when the shape of the particles is a shape elongated in uniaxial direction such as a spheroid, a rod, a needle or the like, it is also preferable to arrange the major axes thereof in a certain direction in the sheet surface. With this arrangement, light is strongly diffused in a direction perpendicular to the major axis direction, so that even if the substrate alone is used, it exhibits anisotropic diffusivity. Therefore, it is preferable that the light diffusing performance as a diffusion sheet is further improved by contributing a strong diffusing direction in the substrate and a strong diffusing direction in the surface having diffuse anisotropy, contributing to the improvement of uniformity and luminance characteristics.

The addition amount of the particles is appropriately set in accordance with the required performance because the appropriate amount differs depending on the refractive index, particle size and shape of the particles, but it is preferably added in the range of 0.01 to 50 wt% 0.01 to 30% by weight, and most preferably 0.1 to 30% by weight.

Examples of the matrix resin used for the diffusible substrate include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexane dimethanol copolymerized polyester resin, isophthalic acid copolymerization Polyester resins such as polyester resins, spiroglycol copolymerized polyester resins and fluorene copolymerized polyester resins; polyolefin resins such as polyethylene, polypropylene, polymethylpentene and alicyclic olefin copolymer resins; polyolefin resins such as polymethyl methacrylate A thermoplastic resin such as acrylic resin, polycarbonate, polystyrene, polyamide, polyether, polyester amide, polyether ester, polyvinyl chloride, a copolymer thereof, or a mixture of these resins can be exemplified. Limited work This is preferably used.

In addition to the thermoplastic resin, a photo-curing resin and a thermosetting resin can be preferably used as the matrix resin of the transparent substrate and the diffusing substrate.

Examples of the photocurable resin include a compound having at least one radically polymerizable group in the molecule, or a compound having cationic polymeric properties. The compound having a radical polymerizing property is a compound which polymerizes or crosslinks by irradiation with active energy rays in the presence of a polymerization initiator which generates a radical by an active energy ray. For example, the compound having at least one ethylenic unsaturated bond Or more, and contains a polyfunctional vinyl monomer in addition to a monofunctional vinyl monomer, and may be an oligomer, a polymer or a mixture thereof. Examples of the compound having at least one cationic polymerizable property in the molecule include compounds selected from one or two or more compounds selected from a compound having an oxirane ring, a compound having an oxetane ring, and a vinyl ether compound.

Examples of the thermosetting resin include an acrylic resin, an epoxy resin, an unsaturated polyester resin, a phenol resin, a urea-melamine resin, a polyurethane resin and a silicone resin, and one kind or a mixture of two or more kinds selected therefrom can be used .

A polymerization initiator is used for the photocurable resin and the thermosetting resin. In the case of a photocurable resin, it is preferable to use a photopolymerization initiator that generates radical species or cationic species by irradiation of an active energy ray in accordance with the wavelength of light and the polymerization type, and in the case of a thermal polymerization initiator, .

When the diffusion sheet of the present invention is a monolayer structure in which the line-shaped uneven pattern / substrate / rough surface is integrated, a line-shaped uneven pattern is formed on one side of the substrate, and the other surface of the substrate is subjected to a roughing treatment.

In the case of a two-layer or three-layer structure in which a layer on which a line-shaped concavo-convex pattern is formed is laminated on a substrate, a material constituting the layer for forming a line-shaped concave- convex pattern may be a thermoplastic resin similar to the matrix resin of the diffusible substrate, The photo-curable resin, and the resin selected from the thermosetting resin. It is also a preferable form to contain particles in the inside while controlling the diffusibility of the line-shaped uneven pattern.

In the case of a two-layer or three-layer structure in which the layer subjected to the roughening treatment is laminated on the substrate, it is preferable to use the above-mentioned material as the layer subjected to the roughening treatment.

It is also preferable to add various additives to each layer of the diffusion sheet of the present invention. As the additive, for example, an antistatic agent, an anti-light agent, a dispersing agent, a compatibilizing agent, a pigment, a dye and the like are preferably used, but other additives are also preferably used within the range not hindering the effect as a diffusion sheet.

The diffusion sheet of the present invention preferably has a total film thickness of 25 to 500 mu m. When the film thickness is 25 mu m or more, the handling property of the sheet is improved, which is preferable. A sheet having a film thickness exceeding 500 mu m can obtain a sheet preferable in view of diffusibility, but is preferably 500 mu m or less from the viewpoint of thinning of the whole backlight unit.

By taking the configuration as described above, the diffusing sheet of the present invention has the following characteristics (1) and (2): (1) the outgoing light intensity distribution 1 of the light ray emitted from the A- 2).

(1) An outgoing angle within the range of 15 to 25 degrees with respect to the outgoing intensity at an outgoing angle of 0 for the outgoing intensity distribution 1 within a plane perpendicular to the longitudinal direction of the convex shape of the A-side is 50% .

(2) An outgoing angle of 50% with respect to the outgoing intensity at an outgoing intensity of 0 for an outgoing intensity distribution 1 in a plane perpendicular to the sheet surface and parallel to the longitudinal direction of the convex shape of the A- 5 °.

In the present invention, the incident angle is an acute angle formed by the normal direction of the sheet surface and the optical axis of incident light, and the exit angle is an acute angle formed by the normal direction of the sheet surface and the optical axis of the emitted light.

The light beam behavior of the diffusing sheet of the present invention is defined as a result of measurement using a goniophotometer GP-200 by Murakami Shikisai Co., Ltd. and the like. The light source of the apparatus was a halogen lamp 12V 50W, and a light amount adjusting filter with an average light transmittance of 1% was used to set the light beam aperture stop 3 (φ about 11 mm) and the light receiving aperture stop 6 (φ about 13 mm) Measure the diffusion sheet by setting the standard sample table with tilting function.

The diffusion sheet of the present invention is characterized in that when the light beam is incident on the B face of the sheet at a light incidence angle of 0 DEG, the light intensity distribution 1 of the light emerging from the A face of the sheet is within a plane perpendicular to the direction of the convex shape of the A face A characteristic in which the luminance and the uniformity are balanced can be expressed by satisfying the range of the output angle of 15% to 25% with the intensity of 50% with respect to the output intensity with the output angle of 0 °. More preferably, the exit angle satisfies the range of 18 to 25 degrees, and more preferably the exit angle satisfies the range of 19.5 to 24 degrees. As described later, when the diffusion sheet of the present invention is mounted on the backlight unit, the direction parallel to the linear portion of the light source and the longitudinal direction of the line-shaped concavo-convex pattern are set parallel to each other, ) Diffuses the image of the light source and improves uniformity. Therefore, when the diffusivity in this direction is insufficient, the light source image is seen through, resulting in a decrease in uniformity. That is, when the angle of incidence at which the intensity is 50% is less than 15, the diffusibility is insufficient and the brightness variation is remarkable, which is not preferable. When the angle at which the intensity is 50% is more than 25 degrees, the diffusibility is sufficient and is preferable from the viewpoint of the uniformity. However, since the light is excessively diffused and the luminance in the front direction is lowered, Range is hard to say.

The diffusing sheet of the present invention is characterized in that when the light beam is incident on the B face of the sheet at a light incidence angle of 0 DEG, the light intensity distribution 1 of the light emitted from the A face of the sheet is perpendicular to the sheet surface, In the plane parallel to the longitudinal direction, the emission angle at which the intensity of 50% with respect to the emission intensity at the emission angle of 0 DEG is satisfied is in the range of 0.5 to 5 DEG, thereby reducing the diffusion of light in the unnecessary direction, Can be achieved. More preferably, the emission angle satisfies 0.5 to 3 degrees, and more preferably, the emission angle satisfies 0.5 to 1.5 degrees. When the diffusion sheet of the present invention is mounted on the backlight unit, since this direction corresponds to the direction parallel to the linear portion of the light source, strong diffusibility is not required. In other words, it is possible to contribute to improvement in luminance while preventing unevenness such as interference fringes by providing a non-diffusing effect while satisfying the above-described range and suppressing diffusion in unnecessary directions as much as possible. When the outgoing angle is less than 0.5 deg., The regularity of the line-shaped concave-convex pattern on the side A is high and unevenness such as interference pattern appears. In addition, when the outgoing angle exceeds 5 DEG, the anisotropic diffusion property of the sheet due to the line-concavo-convex pattern on the side A is insufficient and an efficient diffusion effect can not be obtained.

Thus, when the diffusion sheet of the present invention exhibits anisotropic diffusivity satisfying the emission intensity distribution, a backlight of high luminance and high uniformity can be obtained when the diffusion sheet is mounted on the backlight unit.

The diffusing sheet of the present invention preferably has a diffusivity defined by the following formula in the range of 25 to 40 with respect to the outgoing intensity distribution 1 in a plane perpendicular to the longitudinal direction of the convex shape of the A-plane. I (&thetas;) in the following formula represents the emission intensity of a light beam emitted at an angle [theta].

Diffusion degree = 100 x 0.5 (I (70) + I (20)) / I (5)

Here, the diffusivity is an index indicating the degree of the light diffusing property of the diffusion sheet, and the larger the value is, the more diffuse light is diffused.

The diffusion sheet of the present invention preferably has a diffusion degree of 25 to 40, more preferably 25 to 35 in a direction perpendicular to the longitudinal direction of the convex shape of the A-plane, that is, in the direction of diffusing strongly. When the diffusion degree is 25 or more, spreading of the light diffused by the diffusion sheet is sufficient, and the homogeneity of the backlight can be increased, which is preferable. When the diffusion degree is 40 or less, the diffusibility is excessively strong, so that it is not spread too widely, and even when the backlight is mounted on the backlight, the decrease in the front luminance can be suppressed while increasing the uniformity. That is, by setting the diffusivity in the range of 25 to 40, it is possible to increase the brightness while maintaining high uniformity when mounted on the backlight.

The diffusing sheet of the present invention is characterized in that when a light beam is incident on the B face of the sheet in the plane perpendicular to the longitudinal direction of the convex shape of the A face at an incident angle (10 DEG ≤ 80 DEG) It is preferable that the outgoing intensity distribution 2 emitted from the plane satisfies the following condition (3).

(3) For the outgoing intensity distribution 2 in the plane perpendicular to the longitudinal direction of the convex shape, the outgoing angle? At which the outgoing intensity is the maximum for each of the incident angles? Is? / 3 <? < 3 &lt; / RTI &gt;

Here, the emission angle? Means that the incident light (incident angle?) Is angle-converted and emitted with the strongest intensity at the emission angle?. That is, as shown by the above equations, it is preferable that the diffusion sheet of the present invention has a characteristic of being emitted as an outgoing angle? Toward the front face with respect to the incident angle?.

This is preferable because it contributes to the improvement of the brightness because the angle is converted to the emission angle? Directed toward the front face, so that the light is directed more toward the front than the light ray incident at the high angle. When the outgoing angle? Is less than 2? / 3, the brightness improving effect is exhibited by the angle converting action. Further, when the angle? Is larger than? / 3, the outgoing light does not excessively gather in the normal direction of the sheet surface, and the viewing angle is not narrowed.

Further, the diffusion sheet of the present invention preferably has a total light transmittance of not less than 70% as measured by incidence of light from the B face of the sheet. The total light transmittance is an index related to the light utilization efficiency of the diffusion sheet. When the total light transmittance is extremely low, the utilization efficiency lowers and it is difficult to increase the luminance. In the structure of the diffusion sheet of the present invention, it is preferable that the total light transmittance is 70% or more so that a high luminance can be exhibited when mounted on the backlight unit.

Next, a method of producing the diffusion sheet of the present invention will be described, but other methods are also preferably used without being limited to these methods. Hereinafter, the line-shaped concavo-convex pattern on the A side of the sheet and the method of roughening the B side of the sheet will be described.

As a method of forming the line-shaped concave-convex pattern of the A-side of the sheet, there are (a) a method of transferring a metal mold using a mold, (b) a method of directly processing the surface, (c) a method of coating a coating agent containing particles having anisotropy (D) a method of attaching fabrics to each other, and the like.

(a) A method of transferring a metal mold further includes: (a1) a method in which a metal mold and / or a sheet having a thermoplastic surface on its surface are heated and pressed and pressed to form a film; (a2) a method in which a sheet, on which a light or thermosetting resin is laminated, A method in which the resin is cured by irradiation with an active energy ray or by heating to form a resin, and (a3) a method of transferring a resin charged on a concave portion of the mold in advance onto a substrate.

(B2) a method of cutting by a sandblasting method; (b3) a method of cutting by a laser; and (b4) a method of cutting by a cutting tool, And a method of processing a sheet in which a photocurable resin is laminated on the surface thereof into a desired shape by a method such as lithography or optical interference exposure.

As a method of coating a coating agent containing particles having anisotropy in the shape (c), a method of coating particles having anisotropic shapes such as rods, needles, fibers, spheroids, or coating agents containing these particles, And a method of forming a sheet in which the particles are oriented in a predetermined direction by coating while applying shearing.

(D) As a method for attaching the fabrics having anisotropy to the shape, there is a method of adhering the fabrics having anisotropy to each other on the base by controlling the diameter, density and shape of warp and weft.

Among them, (a) a mold transfer method is more preferable from the viewpoint of productivity, but these processes can be combined, and a desired diffusion sheet can be obtained by appropriately selecting a process.

The method of roughening the B surface of the sheet includes a method of transferring a metal mold using (a) a mold, (b) a method of directly processing the surface, and (e) a method of forming a particle dispersed resin layer have. (e) is the same process as in (c) above. However, it is not necessary to positively use particles having anisotropy in shape here, and for example, a coating agent containing an isotropic spherical shape Coating. Here, the coating agent contains at least one resin selected from a thermoplastic resin, a photocurable resin and a thermosetting resin as a binder resin, diluted with a solvent if necessary, and various additives are added to form a coating film having desired properties can do.

Among them, (e) is a preferable method from the viewpoint of productivity since it has the possibility that it can be formed in line with the film formation of the substrate.

Further, the backlight unit using the diffusion sheet of the present invention includes a plurality of linear light sources in at least a substantially parallel arrangement, a light source in a configuration having a plurality of linear portions in a substantially parallel arrangement, and a light source in which light and shade are observed in a substantially parallel arrangement The diffusion sheet of the present invention is arranged on the upper side of the light source composed of at least one kind selected from the group consisting of the light source and the light source so that the direction parallel to the straight portion of the light source and the longitudinal direction of the convex shape formed on the A- .

As the light source of the direct-type backlight in which the diffusion sheet of the present invention exerts its effect, a light source of a linear shape or a shape having a linear portion (U-shaped tube, W-shaped tube or the like) However, for example, a fluorescent tube is preferably used. It is also a preferred embodiment that the arrangement pitch of the light sources is different within the backlight unit plane. For example, when it is desired to brighten the central portion of the backlight, it is possible to shorten the arrangement pitch of the light sources in the central portion of the screen. In addition, since the area near the frame of the housing becomes dark at the end of the screen, the arrangement pitch can be made short by this arrangement. In this way, it is a preferred embodiment because the effect is obtained by making the arrangement pitch of the light sources unequal for the purpose of adjusting the brightness in the screen.

It is also preferable to provide a reflective member such as a light reflecting film on the lower side (opposite to the screen) of these light sources. By reflecting the light beam emitted from the light source directly downward or the light beam returned from the upper member by the reflecting member to the screen side by the reflecting member, it is possible to contribute to the improvement of brightness by increasing the light utilization efficiency.

The backlight unit of the present invention is characterized in that the longitudinal direction of the convex shape formed on the A side of the diffusion sheet of the present invention is parallel to the direction parallel to the linear portion of the light source. Since the direction perpendicular to the longitudinal direction of the convex shape of the A-plane is the direction in which the sheet exhibits the strongest diffusibility, the anisotropic diffusion property of the diffusion sheet is maximized and the luminance deviation seen in the fluorescent tube image can be efficiently eliminated It becomes.

It is also a preferred embodiment of the backlight unit of the present invention to further use the diffusion sheet of the present invention over the diffusion sheet. Here, as a more preferable installation direction of the diffusion sheet superimposed on the upper side, a direction in which the longitudinal direction of the convex shape formed on the side A and the direction parallel to the linear portion of the light source become parallel or perpendicular can be exemplified. In a parallel arrangement, the anisotropic diffusivity is further enhanced and the uniformity of the backlight unit is improved. In addition, when vertically installed, it is a preferable configuration because the uniformity can be increased in both the vertical and horizontal directions of the backlight unit and the luminance is improved. Since the diffusing sheet of the present invention exhibits anisotropic diffusivity and a light condensing function in a direction perpendicular to the longitudinal direction of the convex shape by the line-shaped concavo-convex pattern of the A side, Can be expected.

In addition to the light source, the diffusion sheet of the present invention, and the above-described light reflection film, various members may be suitably used as the constitution of the backlight unit of the present invention as shown below.

In the backlight unit of the present invention, it is also preferable to provide a light diffusing plate which is a plate-like member containing particles inside the diffusion sheet of the present invention. As a requirement for the backlight unit, in particular, in the case of the direct-type backlight unit, the luminance deviation caused by the shape and arrangement of the light source provided directly under the screen is eliminated, and the entire surface is uniformly bright. Here, the diffusion sheet of the present invention exhibits anisotropic diffusivity, thereby improving the brightness while effectively eliminating the brightness deviation. However, it is preferable to further improve the uniformity of the screen by providing a light diffusion plate containing particles therein It becomes possible. In the backlight unit, the arrangement pitch of the light sources, the distance between the light source and the diffusion sheet, etc., are largely concerned with the screen uniformity. For example, when the arrangement pitch of the light sources is widened or when the distance between the light source and the member is shortened, the luminance deviation becomes more remarkable. Thus, by combining the diffusing sheet of the present invention and the optical diffusing plate, the brightness deviation can be easily solved corresponding to the backlight unit of various structures, which is preferable.

It is also preferable that the light diffusing plate is formed with a plurality of convex shapes having a major axis and a minor axis on at least one surface or a plurality of convex shapes having a stripe shape aligned in the longitudinal direction in substantially one direction. It is preferable that the direction parallel to the linear portion of the light source and the longitudinal direction of the convex shape of the optical diffusing plate are parallel to each other so as to further enhance uniformity of the backlight unit. The shape of the cross section perpendicular to the longitudinal direction of the convex shape is not particularly limited and may be, for example, a circle shape such as a semicircle or an ellipse, a wave shape such as a sinusoidal curve, a prism shape such as a triangle, It can be used preferably.

Further, it is also possible to use a substantially transparent plate-like member instead of a diffusion-type substrate containing particles therein as in the case of the optical diffusion plate. When a transparent substrate having smooth both surfaces is used, a plurality of convex shapes functioning as a support for an optical member such as the diffusion sheet of the present invention and having a longitudinal direction aligned in one direction are formed on the surface, The uniformity and brightness of the backlight unit can be improved similarly.

In the backlight unit of the present invention, it is also a preferred embodiment to provide an optical sheet selected from the group consisting of a diffusion sheet, a prism sheet and a polarized light separation sheet on the upper side and / or the lower side of the diffusion sheet. These optical sheets can be appropriately selected in accordance with the luminance and screen uniformity required for the backlight unit.

As the structure of the backlight unit of the present invention, for example, the pitch of the linear light source, the linear portion, or the linear portion is set to 2p, and the light source and the member (the sheet, film, Etc.) is h, it is preferable to use a structure in which the angle? At which tan? = P / h satisfies 25??? 60.

It is preferable that the diffusing sheet of the present invention is provided with the B surface as the light source side, that is, the light incidence surface, and the A surface with the line-shaped concave and convex pattern formed thereon as the light exit surface. In addition, as described above, if the B surface is subjected to the roughening treatment, the B surface subjected to roughened surface is made to be a light incident surface, thereby improving the light utilization efficiency and improving the luminance. Further, Thereby enhancing the anisotropic diffusion effect. In addition, in the case of a direct-type backlight, since the inside is a cavity structure, a method of extending the housing to the diffusion sheet of the present invention, or a method of using the plate- Is preferably used.

(Example)

Hereinafter, the measuring method and the evaluation method of each of the examples and comparative examples will be described. The measurement was carried out three times with one sample in each of the following measurements, and the average value of the obtained values was evaluated.

(Measurement and evaluation method)

A. Emission intensity distribution, diffusion degree

The optical characteristics of the diffuser sheet were measured using a goniophotometer GP-200 manufactured by Murakami Shikisai Co., Ltd. The diffusion sheet was set on the sample table so that the light beam was incident on the B surface (surface subjected to the roughened surface), and the distribution of the outgoing light intensity from the A surface was measured under the following conditions. Hereinafter, the incident angle is an acute angle formed by the normal direction of the incident surface and the optical axis of incident light, and one direction is positive and the other direction is negative with respect to the normal direction. In addition, the exit angle is an acute angle formed by the normal direction of the exit surface and the optical axis of the outgoing light beam, and positive in one direction relative to the normal direction (the direction in which the extension line of the incident light beam passes is referred to as plus) , Any direction may be positive) and the other direction is negative.

(1) Incident angle 0 ° (incident from normal direction)

When the light beam is incident on the B face of the sheet at an angle of incidence of 0 deg. (Normal direction), the intensity of light output from the A face of the sheet is within the plane perpendicular to the longitudinal direction of the convexity of the A face, And all of the A-plane convex shapes were measured in the plane parallel to the longitudinal direction at 0.1 DEG intervals in the range of the emission angle -90 DEG to 90 DEG.

From the obtained outgoing intensity distribution, the outgoing angle on the positive side which gives the intensity of 50% with respect to the outgoing intensity with the outgoing angle of 0 is read in each direction.

Further, the emission intensity at +5, +20 and +70 degrees from the emission intensity distribution in the plane perpendicular to the longitudinal direction of the convex shape of the A side was read and substituted into the following equation to calculate the diffusivity.

Diffusion degree = 100 × 0.5 × (I (70) + I (20)) / I (5)

In the above formula, I (&amp;thetas;) represents the emission intensity of the light beam at the emission angle [theta].

(2) Incident angle (?) (10 °??? 80 °)

A light beam is incident on the B face of the sheet in a plane perpendicular to the longitudinal direction of the convex shape of the A face of the sheet at an angle of incidence? (10 degrees??? 80 degrees, at intervals of 10 degrees) The intensity of the outgoing distribution in the plane was measured. The measurement range was measured at an emission angle of -90 DEG to 90 DEG at intervals of 0.1 DEG, and an emission angle beta at which the emission intensity became maximum for each incident angle alpha was read.

The conditions common to each measurement were as follows.

Light source: Halogen lamp 12V 50W

Light source side filter: light amount adjustment filter with average transmittance of 1%

Luminous flux Aperture: Setting 3 (φ about 11 mm)

Receiving aperture: setting 6 (φ about 13 mm)

Sample stand: Standard specimen stand with tilting function for reflection transmission (do not use tilting function)

Measurement mode: Transmission.

B. Transmittance, haze

The transmittance and the haze were measured using Hayes computer HGM-2DP, manufactured by Suga Shikenki Co., Ltd. The sample was cut into 100 square mm and measured by setting the light to enter from the B surface (the surface subjected to the roughened surface) of the diffusion sheet.

C. Glossiness

The 60 degree glossiness of the B side (the surface subjected to the roughened surface) of the sheet was measured based on JIS Z8741 using UGV-5B digital gloss gloss system manufactured by Suga Shikenki Co., Ltd. Was measured in two planes in a plane parallel to the plane perpendicular to the longitudinal direction of the convex shape of the A plane on the B plane of the diffusion sheet cut out to 100 square millimeters.

D. Backlight Characteristics

After a lapse of 1 hour from the lighting of a direct-type backlight (housing, reflective film, fluorescent tube portion) of 21 inches (330 mm × 410 mm; diagonal 520 mm) for evaluation, the fluorescent sheet of the present invention 420 mm), and the luminance and uniformity in the front direction were measured using Eye-Scale 3, a luminance variation analyzer manufactured by Eye Systems Co., Ltd.

The mounting direction of the diffusion sheet was set such that the B face was directed toward the light source side and the longitudinal direction of the convex shape of the A face was parallel to the direction parallel to the linear portion of the fluorescent tube.

The measurement position was on a line shifted 25 mm right or left from the center of the backlight in the direction perpendicular to the linear portion of the fluorescent tube.

The luminance was evaluated as an average value of the measurement positions. The uniformity was calculated from the ratio of the maximum value and the minimum value obtained at the measurement position using the following equation.

· Equality (%) = 100 × (maximum value - minimum value) ÷ minimum value

A is less than 2% for the uniformity, A is for more than 2%, less than 3% is greater than 3%, B is less than 5%, B is greater than 5%, and C is greater than 5% .

The following backlight configurations were used.

(Fluorescent tube)

Diameter: 3 mm

Number: 12

Adjacent interval (pitch): 25 mm (= 2p)

Distance between tube center and reflector (lower side): 5 mm

Distance between tube center and member (upper side): 10 mm (= h)

?: 51.3 (tan? = p / h = 1.25)

(Reflective sheet)

Lumirra (registered trademark) 188E60L manufactured by Toray Industries, Inc.

All the above measurements were carried out under conditions of a room temperature of 23 DEG C and a humidity of 65%.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

(Example 1)

Coating agent 1 was coated on one side of a transparent polyethylene terephthalate (PET) base material having a thickness of 188 占 퐉 and dried at 110 占 폚 for 4 minutes to form a 5 占 퐉 particle-containing coating film (roughened surface).

(Coating agent 1)

Acrylic resin A-811 (Aekyung Chemical Co., Ltd.) 30 parts by weight

Acrylic particles MX330 (manufactured by SOUKEN KAGAKU CO., LTD., Particle diameter 3 mu m) 0.8 parts by weight

Methyl ethyl ketone 70 parts by weight

1.5 parts by weight of an antistatic agent.

Subsequently, the coating agent 2 was coated on the side (A side) opposite to the side coated with the coating agent 1 (side B) to form a coating film having a thickness of 30 탆.

(Coating agent 2)

10 parts by mass of Adeka Optomer KRM-2199 (manufactured by Asahi Denka Kogyo K.K.)

1 part by mass of AARON oxetane OXT-221 (manufactured by TOAGOSEI CO., LTD.)

0.25 parts by mass of Adeka Optomer SP170 (manufactured by Asahi Denka Kogyo Co., Ltd.).

A mold having a line-shaped concavo-convex pattern engraved on the surface A of the substrate coated with the coating agent 2 was closely adhered to the surface of the base material to be irradiated with 1 J / m 2 by means of an ultra-high pressure mercury lamp from the side of the substrate to cure the coating agent and release the mold to obtain a diffusion sheet 1 . The line-shaped concave-convex pattern of the A-plane of the obtained diffusing sheet had an irregular shape with roughly a pitch of 3 to 8 탆 and a height of 0.6 to 6 탆.

The properties of the diffusion sheet 1 are shown in Table 1.

Subsequently, an evaluation diffuser sheet (Sumitomo 3M, BEFⅡ), a brightness enhancement sheet (Sumitomo 3M, DBEF-D400), and a light diffusion plate (transmittance of 65% , Luminance and uniformity were measured. The evaluation results are shown in Table 2.

It was found that this backlight unit equipped with the diffusion sheet 1 exhibited high brightness and excellent screen uniformity.

(Example 2)

In Example 1, the shape of the mold was changed to form a diffusion sheet, and an irregularly shaped diffusion sheet 2 was fabricated in which the line-shaped uneven pattern roughly varied in pitch from 3 to 11 탆 and height from 1 to 3 탆. In the same manner as in Example 1 except for this, the backlight for evaluation was installed to measure the luminance and uniformity. The evaluation results are shown in Table 2.

It was found that this backlight unit equipped with the diffusion sheet 2 exhibited high luminance and excellent screen uniformity.

(Example 3)

In Example 1, a lenticular pattern in which a semicircular pattern having a semicircular cross section (radius of 100 mu m) was arranged at a pitch of 200 mu m on the surface of the light diffusing plate (transmittance 65%) instead of the light diffusing plate mounted on the evaluation backlight The formed plate-like member was placed thereon to evaluate the backlight characteristics. Further, the plate-like member was provided so that the side opposite to the side on which the lenticular pattern was formed became the fluorescence observation side. The results are shown in Table 2. As a result, it was found that the brightness and homogeneity were higher than those of Example 1.

(Example 4)

In the same manner as in Example 1 except that a prism shape having an isosceles right triangle (vertex angle of 90 deg., Height of 25 m) perpendicular to the cross section was formed on the surface of the light diffusing plate (transmittance 65%) instead of the light diffusing plate mounted on the evaluation backlight, The formed plate-like member was placed thereon to evaluate the backlight characteristics. Further, the plate-like member was provided so that the side opposite to the side on which the prism shape was formed became the fluorescence observation side. The results are shown in Table 2. As a result, it was found that the brightness and homogeneity were higher than those of Example 1.

(Example 5)

A diffusion sheet 3 was prepared in the same manner as in Example 1 except that Coating agent 2 was coated on the A side in Example 1 to form a coating film having a thickness of 50 mu m and then the metal mold 1 having the following shape was closely contacted to obtain a diffusion sheet. . The properties of the diffusion sheet 3 are shown in Table 1.

(Mold 1)

Unit cross-sectional shape: The shape shown in Fig. 5

A semi-circle having a radius of 50 占 퐉 is formed into a basic shape (aspect ratio (b / a) = 1)

Pitch (p) = 96.6 mu m, height (h) = 37 mu m

Pattern viewed from the side of the mold: Regular stripe pattern.

A plurality of stripe-shaped convex shapes obtained by inverting the mold 1 were formed on the A-plane of the obtained diffusing sheet 3, and the cross section perpendicular to the longitudinal direction of each convex shape had a pitch of 96.6 mu m and a height of 37 mu m.

Subsequently, the evaluation backlight was superimposed on the light source side in the order of a light diffusing plate (transmittance of 65%), a main diffusing sheet, a prism sheet (Sumitomo 3M, BEFⅡ), a brightness enhancing sheet (Sumitomo 3MM, DBEF-D400) , And the luminance and uniformity were measured. The evaluation results are shown in Table 2.

It was found that this backlight unit equipped with the diffusion sheet 3 exhibited high brightness and excellent screen uniformity.

(Example 6)

The diffusion sheet 4 was formed in the same manner as in Example 1 except that a coating film 2 having a thickness of 50 탆 was formed by coating the surface A on the side A and then the metal mold 2 having the following shape was closely contacted to obtain a diffusion sheet. . The properties of the diffusion sheet 4 are shown in Table 1.

(Mold 2)

Unit cross-sectional shape: The shape shown in Fig. 5

A semi-ellipse having a short diameter (a) of 50 占 퐉 and a long diameter (b) of 62.5 占 퐉 is formed into a basic shape (aspect ratio (b / a) = 1.25)

Pitch (p) = 94.8 占 퐉, height (h) = 42.6 占 퐉

Pattern viewed from the side of the mold: Regular stripe pattern.

A plurality of stripe-shaped convex shapes in which the mold 2 was inverted were formed on the A-plane of the obtained diffusing sheet 4, and the cross section perpendicular to the longitudinal direction of each convex shape was a shape having a pitch of 94.8 탆 and a height of 42.6 탆.

Subsequently, the evaluation backlight was superimposed on the light source side in the order of a light diffusing plate (transmittance of 65%), a main diffusing sheet, a prism sheet (Sumitomo 3M, BEFⅡ), a brightness enhancing sheet (Sumitomo 3MM, DBEF-D400) , And the luminance and uniformity were measured. The evaluation results are shown in Table 2.

It was found that this backlight unit equipped with the diffusion sheet 4 exhibited high luminance and excellent screen uniformity.

(Example 7)

Backlight properties were evaluated in the same manner as in Example 3 except that the diffusion sheet 4 (described in Example 6) was used instead of the diffusion sheet 1 in Example 3. The results are shown in Table 2.

(Example 8)

Backlight properties were evaluated in the same manner as in Example 4 except that the diffusion sheet 4 (described in Example 6) was used instead of the diffusion sheet 1 in Example 4. The results are shown in Table 2.

(Comparative Example 1)

Backlight properties were evaluated in the same manner as in Example 1 except that the diffusion sheet of the present invention was replaced by a chromophore diffuser sheet "Light up" 188GM2. Table 1 shows the characteristics of GM2 and the backlight evaluation results. This sheet does not exhibit the anisotropic diffusivity like the diffusion sheet of the present invention and does not satisfy the scope of the present invention with respect to diffusing and angular conversion. The brightness deviation derived from the light source image is not eliminated, The result was a drop.

The diffusion sheet of the present invention can be applied as a thin optical member that exhibits high screen uniformity and high luminance characteristics by being mounted on various display apparatuses, particularly a backlight unit of a liquid crystal display apparatus.

Claims (10)

A plurality of stripe-shaped convex shapes are formed on one side of the sheet, a roughening treatment is performed on the other side of the sheet, Each of the shapes of the convex shapes in the longitudinal direction is aligned in one direction and the shape of each of the shapes in the cross section perpendicular to the longitudinal direction of the convex shape is a half oval shape in which the major axis direction is perpendicular to the sheet surface, Deg.] Or more and 90 deg. Or less, Wherein the roughened surface has a glossiness in the range of 70 to 80 in the direction perpendicular to the longitudinal direction of the plurality of convex shapes and in a range of 115 to 120 in the parallel direction when the 60 degree gloss is measured. Sheet. The diffusing sheet according to claim 1, wherein the semi-elliptical shape has at least an edge angle of not less than 80 占 and not more than 90 占 the aspect ratio of the basic semi-elliptical shape is larger than 1 and not larger than 1.5. A plurality of stripe-shaped convex shapes are formed on one side of the sheet, a roughening treatment is performed on the other side of the sheet, The longitudinal direction of the plurality of convex shapes is aligned in one direction, and each of the shapes of the cross section perpendicular to the longitudinal direction of the convex shape has a shape of at least an edge angle of not less than 80 degrees and not more than 90 degrees Shape, Wherein the roughened surface has a glossiness in the range of 70 to 80 in the direction perpendicular to the longitudinal direction of the plurality of convex shapes and in a range of 115 to 120 in the parallel direction when the 60 degree gloss is measured. Sheet. delete delete delete delete delete A light source having a plurality of linear light sources in a parallel arrangement, a light source in a configuration having a plurality of linear portions in a parallel arrangement, and a light source in which light and dark are observed in a linear shape in a parallel arrangement, The backlight unit according to any one of claims 1 to 3, wherein the diffusion sheet is arranged such that the direction parallel to the straight portion of the light source and the longitudinal direction of the convex shape are parallel. delete

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