JP2010044146A - Light diffusion sheet and backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion sheet in which such a problem is remedied that when the light diffusion sheet obtained by performing printing with ink is applied to a backlight unit and the thick printing is performed with ink in order to make the light diffusion properties thereof higher, the light diffusion properties are enhanced but powder of an ink component is scattered, ink is easily exfoliated when rubbed or ink is apt to be exfoliated when the temperature becomes high due to a light source. <P>SOLUTION: The light diffusion sheet is provided with: a base material; and a pattern-printed part which is formed by printing a predetermined pattern with the ink on (at least) one surface of the base material. A resin layer is formed only on least the upper part of the pattern-printed part. A light diffusing agent can be incorporated in the resin layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light diffusion sheet suitably used as a luminance distribution correction film for a backlight and a method for producing the same. The present invention also relates to a backlight unit including a light diffusion sheet and a light source.

In general, a backlight unit used in a liquid crystal display device or the like is provided with a light diffusion sheet for uniformly emitting light from a light source because the original quality is impaired if there is unevenness in brightness or unevenness. As a light diffusion sheet, for example, a sheet obtained by pattern printing of white ink on a substrate is known (see Patent Document 1). In these light diffusing sheets, white pigments such as titanium oxide are used in the ink, and dot patterns are formed at a higher density as the distance from the light source increases, so that a high light-shielding property is obtained. Can do.
JP 2000-164411 A

However, the light diffusing sheet obtained by printing the ink has a problem that the powder of the ink component (particularly when the pigment is the main component) is scattered or the ink is peeled off. Especially when applied to a backlight unit, if the ink is printed thickly for the purpose of increasing light diffusibility, the light diffusibility will increase, but the ink will be easily peeled off when the ink powder is scattered or rubbed. There is a problem that the ink is easily peeled off when the temperature is increased by the light source.
The present invention is intended to solve the above-mentioned problems, and by providing a resin on a light diffusion sheet on which light diffusible ink is printed, a light diffusion sheet without ink falling off or peeling off is provided. provide.
Moreover, a light diffusing sheet having high light diffusibility is provided by providing a resin containing a light diffusing agent.
Furthermore, it is an object of the present invention to provide a backlight unit having a sufficient luminance by using the light diffusing sheet of the present invention to obtain uniform surface light emission.

The present invention includes the following aspects.
[1] A light diffusion device comprising: a base material; and a pattern printing unit provided in a predetermined pattern on at least one surface of the base material, wherein a resin is formed only at least on the upper part of the pattern printing unit. Sheet.
[2] The light diffusion sheet according to [1], wherein the pattern printing unit is an ink containing a white pigment.
[3] The light diffusion sheet according to any one of [1] to [2], wherein the resin layer contains a light diffusing agent.
[4] A backlight unit comprising a light source and the light diffusing sheet according to any one of [1] to [3] disposed on a light emission side from the light source.

The light diffusion sheet of the invention prevents the printed ink from peeling off and has a sufficient light diffusion property. The backlight unit using the light diffusion sheet of the present invention can obtain uniform surface light emission and has sufficient luminance. Usually, even when two sheets of a pattern printing sheet and a diffusion sheet are required, the same effect can be obtained with one optical member if the light diffusion sheet of the present invention is used.

<Embodiment of the present invention>
(Light diffusion sheet)
An embodiment of the light diffusion sheet of the present invention will be described. Note that the present invention is not limited to this embodiment.
In FIG. 1, the light-diffusion sheet of this embodiment is shown. The light diffusing sheet 1 of the present embodiment has a base material 2 and a pattern printing portion 3 provided in a predetermined pattern on at least one surface of the base material 2, and a resin is provided only at least on the upper side of the pattern printing portion 3. A layer (hereinafter also referred to as a resin portion) 4 is formed. However, there may be a resin other than the upper portion as long as the effect is not impaired.

Also, as shown in FIG. 2, when the pattern printing portion is particularly thick, the resin is formed on at least the upper portion of the pattern printing portion as shown in FIGS. 2 (a) and 2 (b) by the resin portion forming method. The form is preferable in that it can prevent scratches when the ink component powder is scattered or rubbed.
The thickness of the resin layer 4 with respect to the pattern printing unit 3 is not particularly specified. However, it is preferable that the linear transmittance of the resin layer 4 is defined to be 10% or more lower than the linear transmittance of printing when the ink is solid-printed (hereinafter also referred to as a dot pattern).

(Base material)
Although the conventionally well-known thing used in the field | area of the optical member can be used as the base material 2, For example, the member which permeate | transmits visible light, such as a glass substrate and a transparent plastic sheet, is used. Examples of the transparent resin constituting the transparent plastic sheet include polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polycarbonate, acrylic resin, and the like.
Especially, as a base material, it is preferable that it is a translucent base material, and it is further preferable that it is a translucent resin sheet. The light-transmitting light transmission characteristics are not limited as long as they are appropriately adjusted by use. However, the light transmittance in the visible light region is 90% or more in that light from the light source is not lost. Is preferred.
Further, the base material 2 may contain a colorant within a range that transmits visible light, or may contain light diffusing particles uniformly.
The surface of the substrate 2 opposite to the pattern printing 3 may be flat, or an uneven pattern may be formed.
Thus, if an optical function sheet such as a light reflection sheet (light diffusion plate), a light guide sheet (or light guide plate), or a prism sheet is used as a base material, the light diffusion portion (pattern printing portion and light of the present invention) When the diffusing agent is contained, the resin) and these functional sheets can be integrated.
Moreover, in order to improve the adhesiveness with the ink at the time of printing, you may use the base material which gave the corona treatment, the base material which provided the easily bonding layer, and the anchor layer for a base material.

(Pattern printing section and printing method)
In the pattern printing unit 3 of the light diffusion sheet of the present invention, ink is printed in a predetermined pattern. Among them, it is preferable that printing with ink is performed on one side or both sides of the substrate from the viewpoint of luminance uniformity. Moreover, the pattern of one side and one side may be the same or different.
Furthermore, the dots of the pattern printing unit are provided in a predetermined pattern. For example, when a dot having a circular shape on the upper surface of the pattern printing unit is used, the predetermined pattern is appropriately set according to the light diffusibility required for the optical film. In particular, when light diffusibility is strongly required, it is preferable to set the dot area ratio per unit area to be high.
In addition, the printing unit printed with a predetermined pattern diffuses light from the light source and efficiently improves the brightness uniformity. As a result, when the intensity distribution of the light that has passed through the optical sheet is measured, the luminance is uniform. For example, when used in a backlight unit of a liquid crystal display device, increase the dot area ratio per unit area directly above the light source, and gradually decrease the dot density or decrease the dot diameter as you move away from the light source. Adjust to In particular, it is preferable to use a method for adjusting the diameter of a dot because a so-called halftone dot procedure can be used based on the concept of halftone or gray scale.

Moreover, when the light diffusibility calculated | required within an optical film is not uniform, the area ratio of the dot per unit area shall not be uniform according to the calculated | required light diffusibility.
For example, the dot pattern can be a pattern in which dots are uniformly arranged in a partial area of the surface of the base material and dots are not provided in the remaining area.
Furthermore, dot printing with a substantially uniform area per piece on the surface of the substrate has a high light diffusibility region with a large number of dots per unit area, and a low number of dots per unit area than the high light diffusibility region. The pattern provided so that it may have a light diffusible area | region may be sufficient.
Furthermore, in the dot-like pattern printing unit having the same number per unit area on the surface of the base material, a high light diffusive area having a large area of dots per one piece, and more per one than the high light diffusible area A pattern having a low light diffusing region with a small dot area may be used.
The dot pattern is a pattern in which the area ratio of dots per unit area gradually increases along one direction of the base material, or a pattern in which the area ratio of dots changes periodically along one direction of the base material. There may be. Further, the pattern may be a pattern in which dots are uniformly distributed over the entire surface of the substrate.

As another method of adjusting the uniformity, there is a density gradation in which a solid pattern printing unit is provided and the thickness of the pattern printing unit is adjusted. In other words, it is a density gradation formed in the area directly facing the light source, and the thickness of the pattern printing part immediately above the light source is increased, and the thickness of the pattern printing part is gradually reduced as the distance from the light source increases. Further, it is possible to level the light passing through the optical sheet.

Further, when the light diffusibility required in the optical film is not uniform, the thickness of the solid pattern printed portion is not uniform in accordance with the required light diffusibility.
For example, the solid pattern printing unit may be a pattern in which a certain thickness is printed on a part of one surface of the base material and a printing unit is not provided in the remaining region.
Further, the substrate has a high light diffusibility region in which the thickness of the solid pattern printing portion is large and a low light diffusibility region in which the thickness of the solid pattern printing portion is smaller than that of the high light diffusibility region. The pattern may be provided as described above.
Also, a pattern in which the thickness of the solid pattern printing part gradually increases along one direction of the base material, or a pattern in which the thickness of the solid pattern printing part changes periodically along one direction of the base material It may be.
Further, the solid pattern printing portion may be provided on the entire surface of the substrate with a certain thickness.

In the present invention, the gradation is adjusted by arbitrarily changing the linear light transmittance of the light diffusing ink in the range of 0% to 100%. Here, the linear light transmittance may be measured by a known optical instrument, but it is preferable to use a haze meter based on JIS-K7105 for simple measurement.
The thickness of the pattern printing portion by ink can be adjusted by the printing method (conditions and number of times). Among these, a range of 0.5 μm to 100 μm is preferable. If the thickness of the printing part is 0.5 μm or more, the light diffusibility can be further increased. If it is 100 μm or less, pattern printing can be performed with high accuracy.
There are no restrictions on the printing method, and letterpress printing (including flexographic printing), intaglio printing (including gravure printing), flat printing (including offset printing), stencil printing (including screen printing), and plateless printing are available. Illustrated. Plateless printing refers to a method in which a pattern is directly formed on a substrate. Ink jet printing, which has been developed in recent years, and an electrophotographic method using dry or wet toner are known.
The printing dot shape is not particularly limited, but the pattern shape is preferably a repeating unit having a fixed shape. Examples of the shape include dots such as a dot, a circle, a triangle, a square, an ellipse, and a hexagon. And a belt-like shape. A circular dot is preferable because it has a general shape. The size of the dot is preferably in the range of 5 to 500 μm in the case of a circular shape, for example.

The type of ink is not particularly limited, but an ink having a large difference from the refractive index of the resin provided around the pattern printing portion is preferable in order to enhance the light diffusibility effect. Accordingly, a white ink mainly composed of a material having a high refractive index is preferable. The white ink reflects a part of the light, and the remaining light is transmitted and diffused. Therefore, the white ink is preferable from the viewpoint that the light diffusibility can be adjusted without decreasing the luminance. In addition, black ink, gray ink, silver ink, and the like can be used. As a representative black ink, an ink mainly composed of carbon black can be mentioned, and it is only necessary to consider the light shielding effect. Therefore, it is expected that the light transmittance can be easily adjusted and the optical design can be easily performed. As the gray or silver ink, for example, a metal powder-containing ink prepared by containing gray metal powder such as aluminum, silver, palladium, or zinc or silver metal powder can be used.
The ink composition contains a solvent, a pigment, a dispersant, and a resin as a fixing agent on the surface of the object as basic components.
As white particles in the ink composition, titanium oxide (TiO ₂ , titanium white), silica (SiO ₂ ), calcium carbonate, talc, clay, aluminum silicate, basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , silver White), zinc oxide (ZnO, zinc white), strontium titanate (SrTiO ₃ , titanium strontium white), barium sulfate, inorganic glass, and the like can be used alone or in a mixed system, but are not limited thereto.
Titanium oxide in particular has a dispersion stability because it has a lower specific gravity than other inorganic white pigments, has a large refractive index, an excellent optical scattering property, and is chemically and physically stable. For this reason, since the hiding power and optical scattering property as a pigment are large, it is preferable to use titanium oxide as a main component as the inorganic white pigment used in the present invention. The white pigment can be mixed for the purpose of adjusting the color of the diffused light. The mixing ratio of the white pigment is preferably 30 to 80% by mass of the entire ink composition. The white pigment other than titanium oxide is preferably used in an amount of up to about 30% of the total pigment for the purpose of dispersion aid, if necessary.

Examples of the resin in the ink composition include ketone resin, sulfoamide resin, maleic acid resin, ester gum, xylene resin, alkyd resin, rosin, polyvinyl pyrrolidone, polyvinyl butyral, acrylic resin, melamine resin, cellulose resin, vinyl resin, and phenol. Resins, ester resins and the like can be used, and among them, acrylic resins can be preferably used. The organic solvent in the ink composition is used for the purpose of dissolving the resin and adjusting the viscosity, and is an aromatic hydrocarbon solvent such as toluene, xylene, ethylbenzene, n-hexane, n-heptane, isoheptane, n-octane. In addition, aliphatic hydrocarbon solvents such as isooctane, cycloparaffin solvents such as methylcyclohexane and ethylcyclohexane, and the like can be used alone or in the form of a mixture. The usage-amount of an organic solvent is about 30-80 mass% of the whole ink composition.

(About resin layer)
Examples of the resin layer formed on at least the upper part of the pattern printing portion used in the present invention include the following resins. Among these, in order to enhance the light diffusive effect, a resin having a large difference in refractive index between the resin and the pattern printing layer is preferable, and the difference in refractive index is preferably 0.1 or more. More preferably, a highly transparent resin is preferred in order to increase the light diffusibility of the ink.
The resin used in the present invention may be the same as the resin used for the ink. Moreover, a UV curable resin, a thermosetting resin, etc. can be used for resin according to a manufacturing method.
Here, the kind and refractive index of the resin used in the present invention are shown. Examples of the refractive index include the document “Plastics” Vol. 52, no. The values are known values described on pages 8 and 98, Polymer Handbook pages 453 to 457, and the like.
Examples of the resin include high refractive index polyvinylidene chloride (refractive index: 1.6 to 1.63), amorphous polyester (1.62), polystyrene resin (1.59), and polycarbonate (1.59). , Polyvinyl chloride (1.54), urea resin (1.54), urethane resin (1.53 to 1.67), olefin-maleimide alternating copolymer (1.53), polyacrylonitrile (1.52) , Polymethacrylonitrile (1.52), poly (cyclohexane) (1.51), methacrylate resin (1.51), polyvinyl alcohol resin (1.49 to 1.53), alicyclic olefin resin (norbornene) System), polymethyl methacrylate (1.49), polyacetal (1.48), cellulose triacetate (TAC) (1.47), poly (1,3-si Clohexadiene) (1.45), vinyl acetate, ultra low refractive index amorphous fluororesin (1.34), ketone resin, sulfoamide resin, maleic resin, xylene resin, alkyd resin, rosin, polyvinylpyrrolidone, Examples include, but are not limited to, polyvinyl butyral, acrylic resins, melamine resins, ester resins, and copolymers thereof. If the refractive index is appropriate, these resins may be used in combination. Moreover, the commercially available varnish containing said resin may be sufficient. Varnish is generally a mixture of resin, dry oil (oil that gradually oxidizes and solidifies in air: linseed oil, etc.) and solvent, and is completely or almost colorless and transparent.

(Light diffusing agent)
In the resin of the present invention, it is preferable to contain a light diffusing agent because transmitted light can be diffused more.
As the light diffusing agent used in the present invention, a conventionally known one may be used as long as it has the property of diffusing light rays. Here, the light diffusing agent is capable of refracting and diffusing light according to the difference in refractive index from the surroundings.
The average particle size of the light diffusing agent is preferably 100 nm to 2000 μm, particularly preferably 300 nm to 200 μm.
Examples of the light diffusing agent include organic particles, inorganic particles, organic or inorganic hollow particles, expanded particles, porous particles, and the like.
Among them, a light diffusing agent having a large difference in refractive index from the resin is preferable in order to enhance the light diffusing effect of the light diffusing sheet. Furthermore, in view of the effect of light diffusibility, it is preferable to select a material in which the difference in refractive index between the light diffusing agent and the resin is 0.1 or more.

As the inorganic particles, inorganic glass beads, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, titanium oxide, calcium carbonate, talc, clay, or a mixture thereof can be used.
Organic particles include high refractive index episulfide resin (1.70), thiourethane resin (1.67), polyvinylidene chloride (refractive index 1.6 to 1.63), amorphous polyester (1.62). ), Polystyrene (1.59), polycarbonate (1.59), polyvinyl chloride (1.54), urea resin (1.54), urethane resin (1.53 to 1.67), olefin-maleimide alternating Polymer (1.53), polyacrylonitrile (1.52), polymethacrylonitrile (1.52), poly (cyclohexane) (1.51), polypropylene (1.50), methacrylate (1.51), Polyvinyl alcohol (1.49 to 1.53), alicyclic olefin resin (norbornene), polymethyl methacrylate (1.49), polyacetal (1.4 ), Poly (1,3-cyclohexadiene) (1.45), and vinyl acetate. A copolymer of these resins or a mixture thereof may be used as long as the refractive index is suitable. Of these, inorganic particles are preferred as the light diffusing agent because of its low swelling property with ink.

The shape of the light diffusing agent is not particularly limited. For example, a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a daruma particle (for example, a particle obtained by joining crosslinked polystyrene particles and crosslinked methacrylate particles), a plate Shape, scale shape, fiber shape and the like, and beads are preferable in consideration of light diffusibility. By using beads, the light diffusion function can be further improved. Further, hollow particles or expanded particles may be used.
Here, the hollow particles are configured to refract and diffuse light by the difference in refractive index between the air (refractive index 1.0) in the hollow beads and the surroundings.
Specifically, cross-linked polymethyl methacrylate (refractive index 1.49, for example, Sekisui Chemical Co., Ltd. MBX series), cross-linked polystyrene (refractive index 1.59, for example, Sekisui Chemical Co., Ltd. SBX series), commercially available uncrosslinked acrylic hollow particles And hollow particles of styrene and methyl methacrylate copolymer. Examples of the expanded particles include acrylonitrile-based resins (for example, Sekisui Chemical Co., Ltd. EHM series) which are expanded by heat.
The blending amount of the light diffusing agent is preferably 0 to 80 parts by mass, particularly preferably 5 to 60 parts by mass with respect to 100 parts by mass of the resin. In the case of 0 part by weight, there is no light diffusing agent and there is an effect of preventing ink peeling, but an auxiliary light diffusing effect by the light diffusing agent cannot be expected. If it exceeds 80 parts by mass, it may be difficult to apply the resin composition for forming the light adjustment pattern.

(Other components of the resin layer)
The resin layer used in the present invention contains a resin as a main component, but may contain a deterioration inhibitor, a dispersant, a plasticizer, a stabilizer, a colorant, etc., as necessary, as long as the effect is not impaired. it can.

<Method for producing light diffuser sheet>
Next, about the manufacturing method of the said light-diffusion sheet 1, a specific example is given and demonstrated about the manufacturing method of the pattern printing part by ink.
The light diffusing sheet of the present embodiment is first provided with a predetermined pattern printing portion by the above-described printing method using ink. Next, a resin is formed on the upper part of the pattern printing unit.
As a method for forming the resin layer, a paint used for the resin is prepared and applied by the following application method.
Examples of the resin coating application method include bar coating, air doctor coating, blade coating, squeeze coating, air knife coating, roll coating, gravure coating, transfer coating, comma coating, and smoothing. Coating method, micro gravure coating method, reverse roll coating method, multi-roll coating method, dip coating method, rod coating method, kiss coating method, gate roll coating method, falling curtain coating method, slide coating method, fountain coating method, and slit die coating Law.
As another method, the paint used for the resin layer can be printed only on the upper part of the pattern printing unit by a printing method (for example, a screen printing method, an offset printing method, or the like). By this method, a resin layer can be formed at a predetermined place.

<Application of light diffusion sheet>
In addition, the light diffusion sheet obtained by the above production method can be suitably used as a luminance distribution correction film for backlight that is provided in a liquid crystal display device, signboard illumination, and the like. Specifically, it can be used for a direct type backlight unit, a sidelight type backlight unit, and the like.
Hereinafter, an embodiment in which the light diffusion sheet obtained by the above manufacturing method is used for a direct type backlight unit or a sidelight type backlight unit will be described.

(Direct type backlight unit)
FIG. 3 shows an embodiment in which the backlight unit is a direct type backlight unit. The direct type backlight unit 3 includes a light diffusion sheet 1 and a light source 6 such as a cold cathode tube or an LED.
The light diffusing sheet 1 used in the direct type backlight unit 5 has a band-shaped light diffusing region A and a non-light diffusing region B. The light diffusing region A is provided with a large number of identical dot-shaped pattern printing portions (ink portions) on one surface of the substrate, and the formation density of the pattern foam layer is wide from the center in the width direction of the light diffusing region A. It becomes smaller as it goes to both ends of the direction. Therefore, the light diffusibility is highest at the center of the light diffusible region A in the width direction.
The non-light diffusing region B is a region of the base material only.
In the direct type backlight unit 5 of the present embodiment, the center in the width direction of the light diffusing region A is disposed immediately above the light source 6.

In the direct type backlight unit 5, the amount of light reaching from the light source 6 increases at a portion immediately above the light source 6 of the light diffusion sheet 1, and the light reaching from the light source 6 at a portion away from the light source 6. The amount of light decreases.
In the present embodiment, since the center in the width direction of the light diffusible region A is disposed immediately above the light source 6, the light diffusibility of the light diffusing sheet 1 at a portion where the amount of light reaching the light source 6 is large. Is high. Therefore, light can be diffused in the non-light diffusing region B located in the portion of the light diffusing sheet 1 away from the light source 6. As a result, the amount of light emitted from the light source 6 can be corrected so as to be uniform in the surface direction, so that uniform surface light emission can be obtained. Moreover, since the light-diffusion sheet 1 has suppressed the light transmittance fall, the direct type backlight unit 5 has sufficient brightness | luminance.

(Side light type backlight unit)
FIG. 4 shows an embodiment in which the backlight unit is a sidelight type backlight unit. The sidelight type backlight unit 7 includes a light diffusion sheet 1 and a light source 6 adjacent to one side surface of the light diffusion sheet 1.
The light diffusing sheet 1 used in the sidelight-type backlight unit 7 has a pattern printing unit per unit area (from the first side surface adjacent to the light source 6 toward the second side surface facing the first side surface ( The ink area is printed so that the area ratio gradually increases. Therefore, the light diffusibility increases from the first side surface toward the second side surface.

In the sidelight type backlight unit 7, the amount of light reaching the light source 6 from the first side surface of the light diffusion sheet 1 increases most, and the amount of light reaching the light source 6 decreases as the distance from the first side surface increases. .
However, in the light diffusing sheet 1 in the present embodiment, the light diffusibility increases as it goes from the first side surface to the second side surface, and therefore the amount of light emitted on the first side surface side can be suppressed. The amount of emitted light can be increased as the distance from the first side surface increases. As a result, the amount of light emitted from the light source 6 can be corrected to be uniform in the surface direction, so that uniform surface light emission can be obtained. Moreover, since the light-diffusion sheet 1 has suppressed the light transmittance fall, the sidelight type backlight unit 6 has sufficient brightness | luminance.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1
In this example, a light diffusing sheet 1 indicated by 12 in FIG. 1 is produced, and a direct type backlight unit is obtained using the light diffusing sheet 1.

In Example 1, a light diffusion sheet 1 indicated by 12 in FIG. 1 was produced.

(Ink pattern printing layer + transparent resin layer by pattern printing)
Using a multi-color sheet-fed printing machine, a predetermined halftone pattern is printed twice on the base sheet using white ink and transparent medium by offset printing with water. An optical film having a “pattern portion” was obtained.
As the base sheet, a polyethylene terephthalate sheet (manufactured by Toyobo Co., Ltd., Cosmo Shine A4300, thickness: 100 μm) was used.
In pattern printing, a predetermined halftone gradation pattern was printed with an AM screen 100 L / in (square halftone dots). Ink was cured with UV irradiation of 300 mJ / cm ² using FDO New Aoguchi T White HF1 B and FDO New Medium HF1 B (both manufactured by Toyo Ink Manufacturing Co., Ltd.), UV inks for offset printing with water. .

(Evaluation as an optical sheet)
The obtained light diffusing sheet was attached so that the light diffusing region was located immediately above the light source composed of a cold cathode tube, to produce a direct type backlight unit.
When the light source of this direct type backlight unit was made to emit light, uniform surface emission was obtained.

(Ink peeling test and results)
When the test similar to Example 1 was done, the test result of the obtained light-diffusion film was (circle).

(Example 2)
In this example, a light diffusing sheet 1 indicated by 12 in FIG. 1 is produced, and a direct type backlight unit is obtained using the light diffusing sheet 1.

(Formation of ink pattern printing part)
Screen polyethylene (Recure 4701VX Medium White, manufactured by Nippon Paper Chemicals Co., Ltd .: titanium oxide (rutile type: refractive index 2.71)) is screen-printed in a predetermined pattern on a polyethylene terephthalate sheet as a base material, and the UV irradiation light quantity is 150 mJ / UV-cured at cm ^2. A sheet on which a pattern printing portion (thickness 3 μm) was formed with ink was obtained.

(Formation of resin layer containing light diffusing agent)
In pattern printing, a predetermined halftone gradation pattern was printed with an AM screen 100 L / in (square halftone dots). The ink printing part added polystyrene spherical particles (refractive index 1.59: particle diameter 5 μm) as a light diffusing agent to a polymethyl methacrylate resin (refractive index 1.49) diluted with a solvent and dispersed by stirring. A paint was obtained.
By the above operation, an optical film in which a pattern printing portion coated with a resin was provided on one surface of the substrate was obtained.

(Evaluation as an optical sheet)
The obtained light diffusing sheet was attached so that the light diffusing region was located immediately above the light source composed of a cold cathode tube, to produce a direct type backlight unit.
When the light source of this direct type backlight unit was made to emit light, uniform surface emission was obtained.
(Ink peeling test and results)
As a result of conducting an ink peeling test similar to that of Example 1 on the light diffusion sheet in which the ink pattern printing part to which the resin was applied was provided on one surface of the base material, the result was ◯.

(Example 3)
In this example, a light diffusion sheet 1 indicated by 12 in FIG. 1 was produced.
A sheet on which an ink pattern printing part was formed was obtained in the same manner as in Example 1.
A resin paint was prepared by adding spherical particles of inorganic glass (refractive index 1.60: particle diameter 5 μm) as a light diffusing agent to polymethylmethacrylate resin diluted with a solvent (refractive index 1.49) and dispersing it. . Screen printing (the same pattern as the pattern of the ink printing part) similar to Example 1 was performed on the surface of the printing part of the obtained sheet using a resin paint to form a resin part.

(Evaluation as an optical sheet)
The obtained light diffusing sheet was attached so that the light diffusing region was located immediately above the light source composed of a cold cathode tube, to produce a direct type backlight unit.
When the light source of this direct type backlight unit was made to emit light, uniform surface emission was obtained.

(Ink peeling test and results)
As a result of conducting an ink peeling test similar to that of Example 1 on the light diffusion sheet in which the ink printing layer in which the resin was applied on the ink part was provided on one surface of the base material, the result was ◯.

(Comparative Example 1)
When an ink peeling test was performed on a sheet printed with ink in the same manner as in Example 1 (when the resin layer was not applied), the result was Δ.

(Comparative Example 2)
When the ink peeling test was performed on the sheet printed with the ink in the same manner as in Example 3 (when the resin layer was not applied), it was x.

It is a figure which shows embodiment of the light-diffusion sheet of this invention. It is an image figure of the ink part and resin layer of the light-diffusion sheet of this invention. It is the schematic which shows one Embodiment of the backlight unit of this invention. It is the schematic which shows other embodiment of the backlight unit of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusing sheet 2 Base material 3 Ink printing part 4 Resin layer 5 Direct type backlight unit 6 Light source 7 Sidelight type backlight unit A Light diffusing area B Non-light diffusing area

Claims (4)

  A light diffusing sheet comprising: a base material; and a pattern printing unit provided in a predetermined pattern on at least one surface of the base material, wherein a resin is formed only at least on the upper part of the pattern printing unit.   The light diffusing sheet according to claim 1, wherein the pattern printing unit is an ink containing a white pigment. The light-diffusion sheet in any one of Claims 1-2 which contains the light-diffusion agent in the said resin.   The backlight unit which comprises a light source and the light-diffusion sheet in any one of Claims 1-3 arrange | positioned at the light emission side from this light source.

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