KR101345177B1 - Optical sheet, method for producing optical sheet, and liquid crystal display backlight unit - Google Patents

Abstract

The present invention forms a primer layer that improves the adhesion between the light diffusing layer and the support between the light diffusing layer and the transparent support, thereby having excellent processing aptitude, enabling reduction of dust in processing and assembly processes, and achieving an improvement in yield. And improving the wettability of the light-diffusion layer coating liquid to the support body at the time of application | coating, and improving the quality, such as high brightness of front brightness and uniformity of brightness, maintaining a haze, the optical sheet and its manufacturing method, And a backlight unit for a liquid crystal display device. This invention is an optical sheet provided with the support body and the primer layer which has a light-diffusion layer on this support body, and this light-diffusion layer contains 50 mass% or more of resin similar to resin which the said light-diffusion layer contains as solid content. The form in which the refractive index difference of a light-diffusion layer and a primer layer is 0.05 or less, the form which contains 50 mass% or more of the same coating solvents of the light-diffusion layer and a primer layer, the form whose film thickness of a primer layer is 0.05-2.0 micrometers, etc. are preferable.

Description

Optical sheet, its manufacturing method, and backlight unit for liquid crystal display devices {OPTICAL SHEET, METHOD FOR PRODUCING OPTICAL SHEET, AND LIQUID CRYSTAL DISPLAY BACKLIGHT UNIT}

1 is a schematic cross-sectional view showing an example of a direct type backlight unit.

2 is a schematic cross-sectional view showing an example of the optical sheet of the present invention.

INDUSTRIAL APPLICATION This invention is used for liquid crystal display devices, such as a mobile telephone, a PC monitor, a television, a liquid crystal projector, and has the outstanding viewing angle characteristic, the manufacturing method of this optical sheet, and the backlight for liquid crystal display devices using the said optical sheet. It's about the unit.

Background Art In recent years, the liquid crystal display device has been rapidly developed, and is used in mobile phones, PC monitors, televisions, liquid crystal projectors, and the like.

In general, the liquid crystal display includes display modes such as twisted nematic (TN) mode, vertical alignment (VA) mode, in-plane switching (IPS) mode, optically compensated bend (OCB) mode, and electrically controlled beirefringence (ECB) mode. It is a liquid crystal display device which expresses a character or an image by operating a liquid crystal, electrically controlling the light which passes through the said liquid crystal, and displaying a difference of contrast on a screen.

Generally, such a liquid crystal display device is known as a thin film transistor (TFT) -LCD, and the TN mode is the mainstream as the liquid crystal operating mode of the TFT-LCD. In recent years, as the development of the use of liquid crystal displays progresses, the demand for high contrast has increased, and researches on the liquid crystal display of the VA mode have been actively conducted.

These liquid crystal display devices are widely used with backlights for illuminating the liquid crystal layer from the back side, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. The direct type backlight unit is used for a larger liquid crystal display device, and generally, as shown in FIG. 1, a rod-shaped light source 16 on a light box 17 having a reflective sheet (not shown) attached inside. Is installed, and several kinds of optical sheets are provided thereon. As a light source of the direct type backlight unit, a cold cathode tube (CCLF) is generally used. Directly above the light source (the liquid crystal cell side), a diffusion plate 15 for reducing the lamp deviation is provided, and optical sheets such as the diffusion sheet 14, the prism sheet 13, and the polarization selective type brightness enhancement film 12 are provided. It is installed more. The kind and the number of these optical sheets are not limited to the combination shown in FIG. 1, It is possible to change a combination as needed.

Among these, the diffusion sheet diffuses the light from the light source, further reduces the luminance deviation, condenses the light upwards (liquid crystal cell side), and increases the luminance (front luminance) in this direction (front side). Have Generally, as shown in FIG. 2, a diffusive optical sheet is laminated | stacked on the transparent synthetic support body 22 and the surface of this support body 22, and is mainly a light-diffusion layer which has light diffusivity and light condensation ( 25).

This light-diffusion layer 25 has the structure which organic particle | grains disperse | distributed generally in resin which consists of organic polymers (refer Unexamined-Japanese-Patent No. 6-67003).

Further, if necessary, a primer layer for maintaining adhesion between the support and the light diffusing layer or a back surface provided with a sliding property for preventing interference color, preventing Newton ring, and improving handleability on the surface of the support on the opposite side thereof. A layer is provided (see Japanese Patent Laid-Open No. Hei 6-230230 and Japanese Patent No. 3413273).

In particular, the primer layer prevents particles from falling off and improves the wettability during coating of the light diffusion layer in order to maintain the haze, generates burrs during the punching process, and maintains the organic fine particles used in the light diffusion layer. In order to prevent this, it is important to not contaminate the manufacturing process. It is also necessary that there is no influence on light diffusivity.

More specifically, by forming a primer layer that improves the adhesion between the light diffusion layer and the support between the light diffusion layer and the transparent support, it has excellent processing aptitude, enables dust reduction in processing and assembly processes, and improves the yield. Optical sheet which can achieve, and the improvement of the wettability of the light-diffusion layer coating liquid to the support body at the time of application | coating, and the improvement of the quality, such as high brightness of front brightness and uniformity of brightness, maintaining haze, and its manufacturing method, And a backlight unit for a liquid crystal display device has not been provided yet, and a further improvement and development is required.

This invention solves the said problem in the prior art, and makes it a subject to achieve the following objectives. That is, the present invention forms a primer layer that improves the adhesion between the light diffusing layer and the support between the light diffusing layer and the transparent support, thereby having excellent processing aptitude, enabling reduction of dust in processing and assembly processes, and improving yield. To improve the wettability of the light-diffusion layer coating liquid to the support at the time of application | coating, and to maintain haze, and to improve quality, such as high brightness of front brightness and uniformity of brightness, and its manufacturing method. And a backlight unit for a liquid crystal display device.

<1> A support and an optical diffusion layer on the support, wherein the light diffusion layer is provided through a primer layer comprising 50% by mass or more of the same resin as the resin contained in the light diffusion layer in solid content. Sheet.

It is an optical sheet as described in said <1> whose refractive index difference of a <2> light-diffusion layer and a primer layer is 0.05 or less.

It is an optical sheet as described in said <1> in which a <3> light-diffusion layer and a primer layer contain 50 mass% or more of the same coating solvents.

It is an optical sheet as described in said <1> whose thickness of a <4> primer layer is 0.05-2.0 micrometers.

It is an optical sheet as described in said <1> whose hydroxyl value of the same resin which a <5> light-diffusion layer and a primer layer contain is 10 or more and 100 or less.

It is an optical sheet as described in said <1> provided with a white layer in the surface side which does not have a light-diffusion layer and a primer layer of a <6> support body.

The same resin which a <7> light-diffusion layer and a primer layer contains is an optical sheet as described in said <1> which is an acrylic resin.

It is an optical sheet as described in said <1> by which organic particle is disperse | distributed to a <8> light-diffusion layer.

It is the optical sheet as described in said <1> used as a <9> light-diffusion sheet.

<10> The optical sheet according to <1> is manufactured, which is a method for producing an optical sheet.

<11> It is the backlight unit for liquid crystal display devices using one or more optical sheets in any one of said <1>-<9>.

Since the optical sheet of this invention forms on the transparent support body the resin same as resin of a light-diffusion layer as a primer layer, and forms a light-diffusion layer on this primer layer, it improves the adhesiveness of a support body and a light-diffusion layer, and also the light-diffusion layer The wettability to the support can be improved.

Since the backlight unit for liquid crystal display devices of this invention uses the said optical sheet of this invention, it can improve the quality, such as high brightness of front brightness and uniformity of brightness, maintaining a haze.

(Optical sheet)

The optical sheet of this invention has a support body and the light-diffusion layer on this support body, The light-diffusion layer is provided through the primer layer which consists of the same resin as the resin which the said light-diffusion layer contains, and if necessary, such as a white layer, etc. Has more layers.

&Lt; Light diffusion layer &

As the light diffusing layer, it is essential to include fine particles and a binder resin in order to exhibit a light diffusing function, but also to prevent damage during handling, solvent resistance to a solvent for wiping off dirt and contamination on the surface, and the optical sheet. In order to give adhesiveness with the support body at the time of punching into a predetermined form, a crosslinking agent for forming the light diffusing layer into a film is required.

Bridge

As said crosslinking agent, an isocyanate compound is preferable.

As said isocyanate compound, any one or more of the aliphatic isocyanate compound, cyclic aliphatic isocyanate compound, and aromatic polyfunctional isocyanate compound which have 2 or more, preferably 3 or more functional group in a molecule | numerator is used.

As a compound which has 2 or more isocyanate groups in the said molecule, m-phenylene diisocyanate, p-phenylene diisocyanate, 2, 6- tolylene diisocyanate, 2, 4- tolylene diisocyanate, naphthalene-1, 4-di Isocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-biphenyldiisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1 , 4-diisocyanate, xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4'- Diphenylpropane diisocyanate, 4,4'-diphenylhexafluoropropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclo Hexylene-1,2-diisocyanate, cyclohexyl -1,4-diisocyanate, dicyclohexyl methane-4,4'- diisocyanate, 1,4-bis (isocyanate methyl) cyclohexane, 1,3-bis (isocyanate methyl) cyclohexane, isophorone diisocyanate, Lysine diisocyanate etc. are mentioned.

As a polyfunctional isocyanate compound of that excepting the above, using the said isocyanate compound as a main raw material, and making it polyfunctional as an adduct of these trimers, polyols, such as a trimetholol propane, and a bifunctional isocyanate compound, the formalin condensate of benzene isocyanate, Isocyanate compound polymers having polymerizable groups such as methacryloyloxyether isocyanate, lysine triisocyanate and the like can also be used. Among these, those which have xylene diisocyanate or its hydrogenated substance, hexamethylene diisocyanate, tolylene diisocyanate and its hydrogenated substance as main raw materials, and polyfunctional as adducts with trimerol propane, in addition to these trimers, in particular desirable.

These compounds are described in the "Polyurethane Resin Handbook" (Iwata Cage Edition, Daily Industry Newspaper Publication, 1987). Among them, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, trimetholpropane and xylylene-1 Adducts of, 4-diisocyanate or xylylene-1,3-diisocyanate are preferable, and xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, trimetholpropane and Particular preference is given to xylene-1,4-diisocyanate or adducts of xylylene-1,3-diisocyanate.

You may use these polyfunctional isocyanate compounds individually or in mixture of 2 or more types.

Resin containing a functional group which can react with isocyanate

Although isocyanate reacts with water etc. in air, crosslinking reaction advances, but this reaction is slow and productivity is bad for a long time in order to acquire sufficient damage resistance, solvent resistance, and adhesiveness. In particular, when the optical sheet including the light diffusing layer is in the form of a roll, moisture in the air is hard to penetrate into the center of the roll, and thus there is a problem that it takes a longer time to form a film.

Therefore, in order to accelerate hardening reaction by this isocyanate compound, it is effective to add resin containing the functional group which can react with an isocyanate.

As resin containing the functional group which can react with the said isocyanate, resin containing OH, COOH, etc. as this functional group is mentioned. The quantity of these functional groups can be represented by a hydroxyl value, an acid value, etc. Reactivity with isocyanate improves, so that the said hydroxyl group is large, but when too large, there exists a problem that the temperature and humidity change of a cured film become large. In addition, there is a problem that the solvent resistance to alcohol and the like deteriorates.

Therefore, the hydroxyl value is preferably 10 or more and 100 or less, more preferably 15 or more and 80 or less, particularly preferably 20 or more and 70 or less.

The hydroxyl value can be measured, for example, by JIS K1557 esterifying a sample with a pyridine solution of phthalic anhydride and titrating the excess acid with a sodium hydroxide solution.

There is no restriction | limiting in particular as a kind of resin containing the functional group which can react with the said isocyanate, According to the objective, it can select suitably, For example, it contains any one or more of acrylic acid ester and methacrylic acid ester as one component of a monomer. A homopolymer or a copolymer etc. which are mentioned, are mentioned preferably.

As said homopolymer or copolymer, a (meth) acrylic resin, a vinyl acetate resin, an ethylene-vinyl acetate copolymer resin, a vinyl chloride resin, a vinyl chloride- vinylidene chloride copolymer resin, butyral resin, a silicone resin, polyester, for example Resin, vinylidene fluoride resin, nitrocellulose resin, styrene resin, styrene-acrylonitrile copolymer resin, urethane resin, polyethylene, polypropylene, chlorinated polyethylene, rosin derivative and the like. Among them, a (meth) acrylic resin is particularly preferable because the refractive index difference becomes small because the compound is of the same system as the fine particles to be used.

The said (meth) acrylic resin can synthesize | combine resin which has a desired hydroxyl value by copolymerizing a hydroxyl group containing (meth) acrylate monomer.

Examples of such monomers include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl methacrylate 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate. , Methacrylic acid 2-hydroxyethyl, methacrylic acid 2-hydroxypropyl, allyl alcohol, homoallyl alcohol, cinnamon alcohol, crotonyl alcohol and the like.

As for the molecular weight of resin containing the functional group which can react with the said isocyanate, 5,000 or more and 100,000 or less are preferable at a mass mean molecular weight, 20,000 or more and 80,000 or less are more preferable, 30,000 or more and 60,000 or less are especially preferable. When the said mass average molecular weight is less than 5,000, the coating property of a cured film may deteriorate, and when it exceeds 100,000, liquid viscosity may rise and applicability may deteriorate.

- Binder Resin -

In addition to the resin containing a functional group capable of reacting with the isocyanate, another binder resin may be further added for the purpose of adjusting the embedding rate of the particles and adjusting the mechanical properties of the cured film.

There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, For example, the homopolymer or copolymer etc. which contain any one or more of acrylic acid ester and methacrylic acid ester as one component of a monomer are preferable. Can be mentioned.

As said homopolymer or copolymer, a (meth) acrylic resin, a vinyl acetate resin, an ethylene-vinyl acetate copolymer resin, a vinyl chloride resin, a vinyl chloride- vinylidene chloride copolymer resin, butyral resin, silicone resin, polyester, for example Resin, vinylidene fluoride resin, nitrocellulose resin, styrene resin, styrene-acrylonitrile copolymer resin, urethane resin, polyethylene, polypropylene, chlorinated polyethylene, rosin derivative and the like. These may be used individually by 1 type and may be used in combination of 2 or more type. Among these, a (meth) acrylic resin is especially preferable at the point that there is little possibility to melt | dissolve or swell organic particle | grains.

Particulates

There is no restriction | limiting in particular as said microparticles | fine-particles, Although it can select suitably according to the objective, For example, organic particle | grains, such as a polymethylmethacrylate resin particle, melamine resin particle, a polystyrene resin particle, a silicone resin particle, are mentioned preferably. These may be used individually by 1 type and may be used in combination of 2 or more type.

It is preferable that the said organic particle has a crosslinked structure, and especially the polymethylmethacrylate resin particle which has a crosslinked structure is preferable.

Since the fine particles function as a light diffusing agent for diffusing the transmitted light, the mass average particle diameter of the fine particles is preferably 100 μm or less, more preferably 25 μm or less. When the said mass average particle diameter exceeds 100 micrometers, it may become unable to function as a light-diffusion agent. Moreover, when it exceeds 100 micrometers, the sedimentation speed of the particle | grains in a liquid will become large, the risk of particle sedimenting in the conveying liquid piping or a buffer tank during application | coating increases, and it is unpreferable also from the viewpoint of liquid stability.

As addition amount of the said microparticles | fine-particles, 100-500 mass parts is preferable with respect to 100 mass parts of said binder resins, and 200-400 mass parts is more preferable. When the said addition amount is less than 100 mass parts, it may become impossible to function as a light-diffusion agent, and when it exceeds 500 mass parts, it may become difficult to disperse | distribute microparticles | fine-particles.

-combination-

There is no restriction | limiting in particular as resin composition containing the functional group which can react with the said isocyanate after mixing a light-diffusion layer coating liquid and a crosslinking agent liquid, and the said organic particle | grain, According to the objective, Although it can prepare suitably, 25 degreeC a D (n ²⁵⁾ of the difference between the both values of refractive index measured at the line is preferably blended as a combination that is less than 0.20. When the difference of both values of refractive index exceeds 0.20, the influence of the refractive light in particle | grain and resin interface may become large, and front brightness may fall.

In addition, the resin and other resin containing a functional group capable of reacting with the isocyanate, and the light diffusion layer containing the organic particles are generally a crosslinking agent solution containing isocyanate in the light diffusion layer coating liquid prepared by adding and mixing both of them in a suitable solvent. Although it forms by apply | coating on a support body immediately after mixing and drying, it is necessary to prevent organic particle from melt | dissolving at the time of preparation of the said light-diffusion layer coating liquid. Therefore, it is preferable to select suitably the said microparticles | fine-particles from the particle | grains which are not melt | dissolved with respect to the said light-diffusion layer coating liquid, and it is preferable that the solvent of the light-diffusion layer coating liquid mentioned later also suitably selects which does not melt | dissolve the said particle | grains.

In addition, by adjusting the compounding ratio of the fine particles to the resin containing a functional group capable of reacting with the isocyanate and other resins, it is possible to control optical performance such as haze of the optical sheet or the rate of increase in luminance.

On the other hand, 10 mass parts or more are preferable with respect to 100 mass parts of resin, and, as for content in the said light-diffusion layer of the said crosslinking agent, 30-400 mass parts is more preferable. When the said content is less than 10 mass parts, the light-diffusion layer may become easy to be damaged.

Moreover, as for content ratio of resin containing the functional group which can react with the said isocyanate in the said light-diffusion layer, and an isocyanate compound, 1: 1-20: 1 are preferable by mass ratio, and 3: 1-15: 1 are more preferable It is preferable and 5: 1-10: 1 are especially preferable.

Scattering Agent

Moreover, you may add the scattering agent etc. which consist of inorganic particles, as other particle | grains to the said light-diffusion layer.

Like the fine particles described above, the scattering agent functions as a light diffusing agent, so that the light diffusing property can be further improved.

There is no restriction | limiting in particular as said scattering agent, Although a material normally used can be suitably selected and disperse | distributed according to the objective, For example, silica, calcium carbonate, alumina, zirconia, etc. which have a particle diameter of 1-5 micrometers are mentioned. .

There is no restriction | limiting in particular in the addition amount of the said scattering agent in the said light-diffusion layer, As mentioned above, although it can select suitably according to a situation in order to obtain desired total light transmittance and a half value angle, For example, 1-20 mass% desirable.

-menstruum-

There is no restriction | limiting in particular as a solvent used for the said light-diffusion layer coating liquid, Usually, it can select suitably from what is used, and can use.

As said organic solvent, ketones, ethers, alcohols, esters, polyhydric alcohol derivatives, carboxylic acid, etc. are mentioned, for example.

When listed together with specific gravity (shown in parentheses) about these preferable specific examples, as said ketones, for example, acetylacetone (0.975), cyclohexanone (0.945), methylcyclohexanone (0.921), acetone (0.791) , Diethyl ketone (0.816), methyl ethyl ketone (0.805), methyl-n-butyl ketone (0.821), methyl-n-propyl ketone (0.806), and the like.

As said ether, 1, 4- dioxane (1.039), tetrahydrofuran (0.889), etc. are mentioned, for example.

Examples of the alcohols include cyclohexanol (0.949), 3-pentanol (1.046), 2-methylcyclohexanol (0.925), isopropyl alcohol (0.785), ethanol (0.791), and n-butanol (0.810). , t-butanol (0.787), 1-propanol (0.804), methanol (0.792) and the like.

Examples of the esters include isoamyl formate (0.877), isobutyl formate (0.885), ethyl formate (0.917), butyl formate (0.892), propyl formate (0.901), hexyl formate (0.990), and benzyl formate (1.081). ), Methyl formate (0.987), allyl acetate (0.927), isoamyl acetate (0.871), isobutyl acetate (0.873), isopropyl acetate (0.877), ethyl acetate (0.901), 2-ethylhexyl acetate (0.872), Cyclohexyl acetate (0.97), n-butyl acetate (0.876), s-butyl acetate (0.875), propyl acetate (0.887), methyl acetate (0.934), ethyl propionate (0.896), butyl propionate (0.877), methyl propionate ( 0.916), and the like.

Examples of the polyhydric alcohol derivatives include ethylene glycol monoethyl ether acetate (0.975), ethylene glycol monomethyl ether (0.964), ethylene glycol monomethyl ether acetate (1.009), ethylene glycol monomethoxy methyl ether (1.04), Propylene glycol monoethyl ether (0.898), propylene glycol monomethyl ether (0.923), and the like.

As said carboxylic acid, iso butyric acid (0.948), capronic acid (1.049), etc. are mentioned, for example.

Among them, organic solvents having a boiling point of 150 ° C. or less are preferable, and methyl ethyl ketone, cyclohexanone, 1,4-dioxane and ethylene glycol monomethyl ether acetate are particularly preferable from the viewpoint of drying easily after application.

The light diffusion layer is formed by applying the light diffusion layer coating liquid on a primer layer and then drying. The light diffusion layer may be formed of only one layer or two or more layers.

There is no restriction | limiting in particular as a coating method of the said light-diffusion layer coating liquid, Although it can select suitably according to the objective, For example, it can carry out by the coating means used normally, such as a spin coater, a roll coater, a bar coater, a curtain coater.

There is no restriction | limiting in particular as a drying method of the said light-diffusion layer coating liquid, Although the method normally used can be suitably selected, For example, 90-130 degreeC is the point which can be performed for a short time as a drying temperature, and without damaging a material. Preferably, 100-120 degreeC is more preferable. When the said drying temperature is less than 90 degreeC, drying may require a long time, and when it exceeds 130 degreeC, it may damage a material. Moreover, as said drying time, 10 second-5 minutes are preferable, for example, and 1-2 minutes are more preferable.

<Primer Layer>

As said primer layer, 50 mass% or more of resin similar to the said light-diffusion layer is contained as solid content. As said resin, when resin of a light-diffusion layer is acrylic resin, what contains an acrylic resin is especially preferable.

When resin of the said primer layer apply | coats a light-diffusion layer coating liquid, it is preferable to melt-mix and it is preferable that compatibility is high. For this reason, it is preferable to contain the same resin as a light-diffusion layer as mentioned above from a viewpoint of melt mixing, and it is more preferable that a light-diffusion layer coating liquid solvent and a primer layer coating liquid solvent contain 50 mass% or more of the same solvent. Do.

The refractive index difference between the resin of the light diffusion layer and the resin of the primer layer is preferably 0.05 or less from the viewpoint of high luminance.

In addition, when a support body is polyester type, you may use a polyester resin together in order to improve adhesiveness with a transparent support body.

As said polyester resin, For example, the Byron series (for example, Byron 103, 200, 220, 280, 300, GK-140, GK-130, etc.) by the Toyobo company, the Taftone series (for example, Chaos) , NE-382, U-5, ATR-2009, ATR-2010, etc., Eriter series (for example, UE3500, UE3210, XA-8153, KZA-7049, KZA-1449, etc.) made by Unitika The polyester series (for example, TP-220, R-188 etc.) by Kosei Chemical Co., Ltd., the high loss series by Seko Kagaku Co., Ltd., etc. are mentioned.

As for content of the said polyester resin, 2-20 mass% is preferable with respect to the resin component whole quantity of the said primer layer. When the said content is less than 2 mass%, adhesiveness with a transparent support body may be inferior, and when it exceeds 20 mass%, an optical characteristic may deteriorate.

0.05-2 micrometers is preferable and, as for the thickness of the said primer layer, 0.5-1.5 micrometers is more preferable. When the said thickness exceeds 2 micrometers, light transmittance may worsen.

It is preferable to add the organic particle which the said light-diffusion layer contains also from the viewpoint of improving light transmittance and improving viewing angle dependency also to the said primer layer.

There is no restriction | limiting in particular in the addition amount of the said organic particle | grain, Although it can select suitably according to the objective, 250 mass parts or less are preferable with respect to 100 mass parts of said resins, and 0.01-200 mass parts is more preferable.

<White floor>

It is preferable that the said optical sheet has a white layer in the surface side which does not have a light-diffusion layer and a primer layer from a viewpoint of sticking prevention.

The said back layer consists of polyester resin, binder resin, and organic particle | grains, and further contains other components as needed.

What was mentioned above can be used as said polyester resin.

There is no restriction | limiting in particular as said binder resin, Although it can select suitably according to the objective, The homopolymer or copolymer etc. which contain any one or more of acrylic acid ester and methacrylic acid ester as one component of a monomer are mentioned preferably, Polymethyl methacrylate resins are particularly preferred.

There is no restriction | limiting in particular as said organic microparticles | fine-particles, Although it can select suitably according to the objective, Polymethyl methacrylate resin particle, melamine resin particle, polystyrene resin particle, silicone resin particle, etc. are mentioned preferably. Among these, polymethyl methacrylate resin particles are particularly preferable.

It is preferable that content of the said polymethylmethacrylate resin particle is 0.1-2 mass% with respect to the resin component whole quantity of the said white layer. When the said content is less than 0.1 mass%, handleability worsens and it becomes easy to be damaged, or when it introduces into a liquid crystal display device, adhesiveness with other members may deteriorate, and when it exceeds 2 mass%, optical characteristics will deteriorate. It may become.

The said white layer can be formed by the white layer formation process mentioned later.

0.05-5 micrometers is preferable and, as for the thickness of the said primer layer, 0.5-4.5 micrometers is more preferable.

<Support>

There is no restriction | limiting in particular if it is transparent as a support body, and the sheet which has a certain intensity | strength, Although plastic or glass normally used as a support body can be suitably selected and used according to the objective, plastic is especially preferable.

As said plastics, polyester, polyolefin, etc. are mentioned preferably, for example. As said polyester, a polyethylene terephthalate, a polyethylene naphthalate, etc. are mentioned, for example. As said polyolefin, polyamide, polyether, polystyrene, polyesteramide, polycarbonate, polyphenylene sulfide, polyether ester, polyvinyl chloride, polyacrylic acid ester, polymethacrylic acid ester, etc. are mentioned, for example.

Among these, a polyester resin is especially preferable.

There is no restriction | limiting in particular if the thickness of the said support body is the thickness of the range normally employ | adopted as a support body, Although it can select suitably according to the objective, For example, 0.02-4.0 mm is preferable.

In order to improve the adhesiveness with a light-diffusion layer, you may perform a discharge process on the surface of the said support body.

(Method for producing optical sheet)

The manufacturing method of the optical sheet of this invention prepares the primer liquid formed from resin of the same system melt | dissolved in the same solvent system as the light-diffusion layer, and apply | coats it on a transparent support body, At least a microparticle and a hydroxyl value on this primer layer It comprises at least a light-diffusion layer forming step of forming a light-diffusion layer by applying a light-diffusion layer coating liquid containing a resin of 10 to 100 or less, and further comprises other steps as necessary.

In the said light-diffusion layer forming process, the crosslinking agent liquid containing an isocyanate compound at least is added and mixed immediately before apply | coating the said light-diffusion layer coating liquid on a primer layer.

Here, just before the said light-diffusion layer coating liquid is apply | coated on a primer layer, the crosslinking agent liquid containing at least an isocyanate compound is added and mixed in the light-diffusion layer coating liquid containing at least microparticles | fine-particles and hydroxyl value 10 or more and 100 or less. After that, it is applied immediately on the primer layer (mixing the light diffusion layer coating liquid and the crosslinking agent liquid containing the binder and the organic particles immediately before application), and specifically, the fine particles and the hydroxyl value are 10 or more. It means to apply within 30 minutes after adding and mixing a crosslinking agent liquid in the light-diffusion layer coating liquid containing 100 or less. 10 minutes are preferable and, as for the time from the said mixing to apply | coating a light-diffusion layer coating liquid, less than 3 minutes are more preferable. When 30 minutes pass after the said mixing, thickening advances and the conveyance liquid property, applicability | paintability, and application surface shape may deteriorate.

As an apparatus which mixes immediately the said light-diffusion layer coating liquid and a crosslinking agent liquid, an inline mixer, a propeller stirrer, a blade stirrer, a screw stirrer, an ultrasonic stirrer, etc. are mentioned, for example. Among these apparatuses, the use of an inline mixer is preferable because it can be easily installed in an existing pipe, and the mixing with a high viscosity liquid can be performed satisfactorily.

As a commercial item of the said inline mixer, a static mixer (phi 3.4-N60S-523-F, a product made by Noritake Co., Ltd.) etc. can be used preferably, for example.

10-30 mPa * s is preferable and, as for the viscosity (25 degreeC) of the said light-diffusion layer coating liquid (after adding a crosslinking agent) within 30 minutes after adding a crosslinking agent, 15-150 mPa * s is more preferable. When the said viscosity is less than 10 mPa * s, particle settling property may not be maintained, and when it exceeds 200 mPa * s, conveyance liquid property and applicability | paintability may deteriorate, and surface shape may deteriorate.

Here, the viscosity of the light-diffusion layer coating liquid is obtained by mixing the light-diffusion layer coating liquid and the crosslinking agent liquid, and using an E-type viscosity meter (ELD type) manufactured by Tokyo Keiki Co., Ltd. for each coating liquid within 30 minutes. It can measure at 25 degreeC.

<Other Processes>

The manufacturing method of the optical sheet of this invention may also include other processes, such as a white layer formation process, in addition to the process of forming the light-diffusion layer mentioned above.

As said back layer formation process, what apply | coats the white layer coating liquid containing at least polyester resin and polymethyl methacrylate resin particle on a polyester resin film, and forms a white layer is mentioned, for example.

In the manufacturing method of the optical sheet of this invention, when a polyester resin film is used as a support body, and the white layer adjacent to the said support body is formed from the white-layer coating liquid containing a polyester resin, the adhesiveness of a support body and a white layer will improve, It is preferable because it becomes excellent in handleability. Moreover, it is preferable to contain at least polyester resin and polymethyl methacrylate resin particle also in the primer layer coating liquid in a primer layer forming process.

<Structure of Optical Sheet>

There is no restriction | limiting in particular as a structure of the said optical sheet, Although it can select suitably according to the objective, For example, the optical sheet 21 shown in FIG. 2 is mentioned preferably.

The optical sheet 21 shown in this FIG. 2 is provided with the primer layer 23 and the light-diffusion layer 25 in this order on one surface of the support body 22, and is provided with the white layer 24 on the other surface. Is done.

<Applications>

The said optical sheet can be used suitably for liquid crystal display devices, such as a mobile telephone, a PC monitor, a television, and a liquid crystal projector by the advantage. More specifically, the optical sheet can be suitably used for a direct type light source device and an edge light type light source device used as a backlight of the liquid crystal display device.

In addition, since the optical sheet is excellent in adhesiveness and optical characteristics, in the above-described liquid crystal display device, the light diffusion sheet of the backlight unit for a liquid crystal display capable of emitting light with high brightness without variation in the entire surface of the liquid crystal panel. More preferably, it can be used.

(Example)

Hereinafter, although the Example of this invention is described, this invention is not limited to these Examples at all.

(Example 1)

[Production of optical sheet]

The optical sheet was produced by forming on a support body by the following method in order of a primer layer, a white layer, and a light-diffusion layer.

Formation of primer layer

The primer layer coating liquid of the following composition was apply | coated to the single side | surface of the polyethylene terephthalate film of 180 micrometers in thickness as a support body with the wire bar # 10, and it dried at 120 degreeC for 2 minutes, and formed the primer layer which is 0.75 micrometers in thickness.

<Composition of Primer Layer Coating Liquid>

· Methyl ethyl ketone ... 2530 g

50 mass% solution (acrylic acid value 17, acid value 3) of acrylic resin (Acrydick A811BE, the Dainippon Ink & Chemicals Co., Ltd. make). 300g

Cyclohexanone 169.5 g

JULIMER MB-1X (manufactured by Nippon Junyaku Co., Ltd.) 0.54 g

  (Organic particle; Polymethyl methacrylate crosslinking type, spherical ultrafine particle of mass mean particle diameter 6.2 micrometers)

Formation of white layer

The white layer coating liquid of the following composition was apply | coated to the surface on the opposite side to which the primer layer of the said support body was apply | coated with wire bar # 22, and it dried at 120 degreeC for 2 minutes, and formed the white layer which is 1.5 micrometers in thickness.

<White layer coating liquid>

· Methyl ethyl ketone ... 6300 g

20 mass% methyl ethyl ketone solution of acrylic resin (DIAnal BR-80, manufactured by Mitsubishi Rayon Co., Ltd.). 2154 g

Polyester resin (byron 220, manufactured by Toyo Boseki Co., Ltd.). 64.62 g

Cyclohexanone 507 g

JULIMER MB-1X (manufactured by Nippon Kayaku Co., Ltd.). 4.98 g

  (Organic particle; Polymethyl methacrylate crosslinking type, spherical ultrafine particle of mass mean particle diameter 6.2 micrometers)

Formation of Light Diffusion Layer

The liquid is transferred to the primer layer side of the coating material prepared above, and the liquid is transferred to the pump so that the respective flow rates are 9.98 g of the cross-linking agent solution with respect to 100 g of the light-diffusion layer coating liquid, and the liquids are transferred to the static mixer. (phi 3.4-N60S-523-F, manufactured by Noritake Co., Ltd.), and after 3 minutes, the wet coating amount was applied to 64.4 cc / m 2, and dried at 120 ° C. for 2 minutes to form a light diffusion layer. The optical sheet was produced by the above. In addition, the hydroxyl value and acid value of resin in the light-diffusion layer coating liquid were extracted from the catalog (the following example is also the same).

<Composition of the Light Diffusion Layer Coating Liquid>

· Methyl ethyl ketone ... 1,130 g

50 mass% solution (acrylic acid value 17, acid value 3) of acrylic resin (Acrydick A811BE, the Dainippon Ink & Chemicals Co., Ltd. make). 501.6 g

JULIMER MB-20X (manufactured by Nippon Kayaku Co., Ltd.) 421.3 g

  (Organic Particles; Polymethylmethacrylate Crosslinking Type, Spherical Fine Particles with Mass Average Particle Diameter of 18 µm)

F780F (manufactured by Dainippon Ink and Chemical Industries, Ltd.). 0.97 g

  (30 mass% solution of methyl ethyl ketone)

<The composition of the amount of cross-linking agent>

· Methyl ethyl ketone ... 1039 g

Isocyanate compound (Takenate D110N, manufactured by Mitsui Takeda Chemical Co., Ltd.). 352 g

(Example 2)

In Example 1, the acrylic resin of the primer layer coating liquid was changed from Acridic A811BE acrylic resin to A817BA (made by Dainippon Ink & Chemicals Co., Ltd.) 50 mass% solution (hydroxyl group 28, acid value 3). In the same manner as in Example 1, an optical sheet was produced.

(Example 3)

In Example 1, the acrylic resin of the primer layer coating liquid was changed from Acridic A811BE acrylic resin to A814 (manufactured by Dainippon Ink & Chemicals Co., Ltd.) 50 mass% solution (15 hydroxyl value, acid value 2). In the same manner as in Example 1, an optical sheet was produced.

(Example 4)

In Example 1, the optical sheet was produced like Example 1 except having added 15g of Byron 220 to the primer layer coating liquid.

(Comparative Example 1)

The optical sheet was produced like Example 1 except having formed the light-diffusion layer directly on the support body, without forming a primer layer in Example 1.

(Reference Example 1)

In Example 1, the optical sheet was produced like Example 1 except having formed the film thickness of the primer layer into 2.5 micrometers.

(Reference Example 2)

In Example 1, the optical sheet was produced like Example 1 except having changed the methyl ethyl ketone of the light-diffusion layer coating liquid into cyclohexanone.

(Comparative Example 2)

In Example 1, the optical sheet was produced like Example 1 except having changed the primer layer coating liquid into the following prescription.

· Methyl ethyl ketone ... 2680 g

Byron 220... 150g

Cyclohexanone 169.5 g

JULIMER MB-1X (manufactured by Nippon Kayaku Co., Ltd.). 0.54 g

  (Organic particle; Polymethyl methacrylate crosslinking type, spherical ultrafine particle of mass mean particle diameter 6.2 micrometers)

(Comparative Example 3)

In Example 1, the optical sheet was produced like Example 1 except having changed the primer layer coating liquid into the following prescription.

Water 2250 g

Plus coat Z-561 (20 mass% solution; manufactured by Kookagaku Co., Ltd.). 750g

JULIMER MB-1X (manufactured by Nippon Kayaku Co., Ltd.). 0.54 g

  (Organic particle; Polymethyl methacrylate crosslinking type, spherical ultrafine particle of mass mean particle diameter 6.2 micrometers)

(Comparative Example 4)

In Example 1, the optical sheet was produced like Example 1 except having changed the primer layer coating liquid into the following prescription.

· Methanol ... 4,166 g

ZILIMER SP50T (20 mass% solution; manufactured by Nippon Kayaku Co., Ltd.). 1,495 g

Cyclohexanone 339 g

JULIMER MB-1X (manufactured by Nippon Kayaku Co., Ltd.). 1.09 g

  (Organic particle: Polymethylmethacrylate crosslinking type, spherical ultrafine particle of mass mean particle diameter 6.2 micrometers)

[evaluation]

Next, about the produced Example and the comparative example, adhesiveness and optical characteristics were evaluated as follows. The results are shown in Table 1.

&Lt; Evaluation of adhesion &

Ten incisions are inserted into the light-diffusion layer surface of the optical sheet at 1 mm intervals in the longitudinal direction, and an adhesive tape is placed on the incision, and the peeling state of the light-diffusion layer when peeled off quickly by strong force by hand is based on the following three steps. Sensory evaluation.

○: No peeling

△: slightly peeled

×: many peeling

<Evaluation of Optical Properties>

Measurement of haze value (light diffusivity)

Haze value (%) in C light source was measured with the haze meter (made by Sugashi Kenki Co., Ltd.). In addition, a larger value means better light diffusivity.

-Evaluation of front luminance rise rate

The light source used the direct type backlight unit for liquid crystal televisions comprised from a reflective sheet, a cold cathode tube, and a diffuser plate. An optical sheet was mounted on the diffuser plate of the backlight unit, and front luminance K ₁ was measured with a luminance meter (BM-7, manufactured by Topcon). In the same manner, the front luminance K ₀ when there was no optical sheet was measured, and K ₁ / K ₀ was taken as the front luminance rising rate.

Measurement of refractive index difference

The refractive index in the light-diffusion layer and the refractive index in the primer layer were measured, and the refractive index difference between the light-diffusion layer and the primer layer was calculated.

As a specific measuring method of the refractive index, a thin film to be measured is formed on a silicon wafer with a thickness of 3 μm, and using a prism coupler (SPA-4000, manufactured by Pyron Technology), TE (Transverse Electric) mode (S wave), It measured on the conditions of 850 nm.

From the result of Table 1, in Examples 1-4, it turns out that an optical sheet is excellent also in adhesiveness, maintaining favorable optical performance. On the other hand, in the comparative example 1 without a primer layer, optical characteristics and adhesiveness are inferior. In addition, although the adhesiveness was favorable in the reference example 1 and the reference example 2 which changed the solvent in the light-diffusion layer and the primer layer for the thick film thickness solvent, it is inferior to optical characteristic. Similarly, in Comparative Examples 2-4 in which the primer layer was formed of resin other than resin used in the light-diffusion layer, it was confirmed that both optical characteristics and adhesiveness were difficult.

ADVANTAGE OF THE INVENTION According to this invention, it solves the said problem in the past, and forms the primer layer which improves the adhesiveness of a light-diffusion layer and a support body between a light-diffusion layer and a transparent support body, and has the outstanding workability, and the dust in a process and an assembly process Quality, such as high brightness of the front brightness and uniformity of the brightness, while maintaining the haze while improving the wettability of the light-diffusion layer coating liquid to the support during application, and enabling the reduction of the It is possible to provide an optical sheet, a method of manufacturing the same, and a backlight unit for a liquid crystal display device, which can be improved.

The optical sheet of this invention can be used suitably for the liquid crystal display device used for a mobile telephone, a PC monitor, a television, a liquid crystal projector, etc. by the advantage. In addition, since the optical sheet is excellent in damage resistance, solvent resistance, and optical characteristics, in the above-described liquid crystal display device, a backlight unit for a liquid crystal monitor capable of emitting light at high brightness without variation in the entire surface of the liquid crystal panel. As a light-diffusion sheet of, it can be used more preferably.

The manufacturing method of the optical sheet of this invention can ensure the outstanding optical characteristic and adhesiveness by achieving the resin of a light-diffusion layer, and resin of a primer layer the same, can achieve a yield improvement, and can use it suitably for manufacture of an optical sheet. have.

ADVANTAGE OF THE INVENTION According to this invention, it solves the said problem in the past, and forms the primer layer which improves the adhesiveness of a light-diffusion layer and a support body between a light-diffusion layer and a transparent support body, and has the outstanding workability, and the dust in a process and an assembly process Quality, such as high brightness of the front brightness and uniformity of the brightness, while maintaining the haze while improving the wettability of the light-diffusion layer coating liquid to the support during application, and enabling the reduction of the It is possible to provide an optical sheet, a method of manufacturing the same, and a backlight unit for a liquid crystal display device, which can be improved.

Claims (11)

A supporter, and a primer layer and a light-diffusion layer on one side of the support in this order; The primer layer comprises 50% by mass or more of the same resin as the resin contained in the light diffusing layer in solid content, and further contains 50% by mass or more of the same solvent in the respective coating liquids, in which the light diffusing layer and the primer layer are the same. It is obtained by apply | coating the light-diffusion layer coating liquid and primer layer coating liquid to contain respectively, The optical sheet characterized by the above-mentioned. The optical sheet according to claim 1, wherein a difference in refractive index between the light diffusing layer and the primer layer is within 0.05. The thickness of the said primer layer is 0.05-2.0 micrometers, The optical sheet of Claim 1 or 2 characterized by the above-mentioned. The hydroxyl sheet of the same resin which the said light-diffusion layer and a primer layer contain is 10 or more and 100 or less, The optical sheet of Claim 1 or 2 characterized by the above-mentioned. The optical sheet according to claim 1 or 2, wherein a back layer is provided on a surface side of the support, which does not have a light diffusion layer and a primer layer. The optical sheet according to claim 1 or 2, wherein the same resin contained in the light diffusion layer and the primer layer is an acrylic resin. The optical sheet according to claim 1 or 2, wherein organic particles are dispersed in the light diffusion layer. 8. The optical sheet according to claim 7, wherein the primer layer contains organic particles included in the light diffusion layer. The optical sheet according to claim 1 or 2, which is used as a light diffusion sheet. As a manufacturing method of the optical sheet which manufactures the optical sheet of Claim 1 or 2. A primer layer forming step of preparing a primer layer coating liquid containing the same resin and the same solvent as the resin and the solvent contained in the light diffusion layer coating liquid, and applying the primer layer coating liquid on a transparent support to form a primer layer; And a light-diffusion layer forming step of applying the light-diffusion layer coating liquid containing at least organic particles and a resin having a hydroxyl value of 10 or more and 100 or less on the primer layer to form a light diffusion layer. . It is comprised with one or more optical sheets of Claim 1, or 2, The backlight unit for liquid crystal display devices characterized by the above-mentioned.

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