WO2015146732A1

WO2015146732A1 - Laminated film

Info

Publication number: WO2015146732A1
Application number: PCT/JP2015/058002
Authority: WO
Inventors: 前川　茂俊; 裕仁内田; 田中　照也; 博門仲村
Original assignee: 東レ株式会社
Priority date: 2014-03-27
Filing date: 2015-03-18
Publication date: 2015-10-01
Also published as: CN106133560B; CN106133560A; JPWO2015146732A1; TW201540499A; KR20160137992A; JP6679930B2; TWI676551B; KR102373640B1

Abstract

The present invention provides a laminated film that is characterized in that a coating layer that includes particles (a) comprising a resin (A) and having a number average particle size of 4 µm or more is provided on at least one surface of the film, and particles (b) having a number average particle size of 0.1-1 µm, inclusive, are adhered to the surface of said particles (a). Provided are a laminated reflective film and optical sheet with which it is possible to prevent luminance nonuniformity and damage to a light guide plate and reflector plate, said nonuniformity and damage being due to adhesion, even when the temperature inside a liquid crystal television becomes elevated, causing additional weight to be applied to the reflector plate due to warping of the light guide plate and greater friction to occur between the light guide plate and reflector plate due to thermal expansion and contraction of the light guide plate.

Description

Laminated film

The present invention relates to a laminated film provided with a coating layer containing particles, and a backlight unit using the laminated film.

The liquid crystal display uses a backlight that illuminates the liquid crystal cell. Conventionally, depending on the type of liquid crystal display, a relatively small liquid crystal monitor employs an edge light type backlight, while a relatively large liquid crystal television employs a direct type backlight. As these reflective films for a backlight, a porous white film formed of bubbles is generally used (Patent Document 1).

In addition, a white film in which an ultraviolet absorbing layer is laminated in order to prevent yellow discoloration of the film due to ultraviolet rays emitted from a cold cathode tube has been proposed (Patent Documents 2 and 3).

Furthermore, a reflective film in which a layer containing soft beads is laminated on a base sheet layer has also been developed as being particularly suitable for use with a light guide plate having a prism shape added (Patent Documents 4 and 5).

Due to the thinning of LCD televisions, LCD backlights have adopted edge-lighted backlights, and at the same time, edge-lighted backlights have been actively developed. Furthermore, a light-emitting diode (hereinafter abbreviated as LED) is adopted as a light source in order to reduce power consumption and mercury-free.

LCD TVs, unlike notebook computers and desktop monitors, require high brightness and require a large number of LEDs. Therefore, it was necessary to create a case using aluminum with a high thermal conductivity coefficient and take measures for heat dissipation. However, when aluminum is employed, the mechanical strength tends to decrease. Therefore, it has been necessary to form irregularities on the housing by, for example, drawing.

Furthermore, a light guide plate is indispensable as an optical member for an edge light type backlight. As for the light guide plate, the size up to about 25 inch type is sufficient for the conventional notebook personal computer and the desktop monitor, but the liquid crystal television needs 30 to 100 inch type. Therefore, a light guide plate having a convex portion, mainly having dot printing on an acrylic plate, a light guide plate having a concave portion by laser processing or UV transfer method, and the like have been developed.

Therefore, in order to prevent scratches and close contact with the light guide plate, such a reflective plate adjusts the average particle size and burial rate of the soft beads on the surface in contact with the light guide plate to suppress the dropout of the beads, and a white spot defect caused by the close contact A reflective film that suppresses the generation of light, a reflective film that suppresses the occurrence of uneven brightness and white spot defects by controlling the cushion ratio of the film, and a layer containing two types of beads of different hardness are laminated in a base sheet shape Reflected films have been developed (Patent Documents 6, 7, and 8).

On the other hand, by arranging an optical sheet such as a diffusion sheet for diffusing light and a prism sheet for controlling the light traveling direction between the light guide plate and the liquid crystal panel, the efficiency of light output from the light guide plate is improved, Brightness unevenness has been improved. Since these optical sheets are also in contact with the light guide plate, a technique has been developed in which a bead coat is applied to the surface in contact with the light guide plate to prevent scratches and adhesion to the light guide plate (Patent Documents 9 and 10).

JP-A-8-262208 JP 2001-166295 A JP 2002-90515 A Japanese Patent Laid-Open No. 2003-92018 Special table 2008-512719 JP 2009-244509 A International Publication No. 2011/105294 JP 2012-242489 A JP 2008-262147 A JP 2007-86730 A

In recent years, because of the use of steel plates and resins with low thermal conductivity in order to save costs, the temperature inside the case has risen, and the light guide plate repeatedly contracts and expands. In other words, there is a situation in which the reflector and the optical sheet are rubbed strongly.

Therefore, the following subjects are mentioned in a reflecting plate and an optical sheet.
(1) A problem in which the light guide plate, the reflection plate, and the optical sheet are in intimate contact with each other and uneven brightness occurs.
(2) A problem that the light guide plate and the reflection plate and the optical sheet are in close contact with each other, and the reflection plate and the optical sheet are wrinkled due to thermal expansion and contraction of the light guide plate, resulting in uneven brightness. (3) The light guide plate surface is damaged. And / or the problem that the surface of the reflector and the beads of the optical sheet are scraped off to cause luminance unevenness The present invention is that the temperature in the liquid crystal television becomes higher than before, and the reflector due to warpage of the light guide plate more than ever. In addition, the present invention is to provide a laminated film that can prevent unevenness in luminance due to adhesion, damage to the light guide plate, the reflection plate, and the optical sheet even when weighting or rubbing is applied to the optical sheet.

In order to solve this problem, the laminated film of the present invention has the following configuration.
(1) A coating layer containing particles (a) having a number average particle diameter of 4 μm or more made of resin (A) is provided on at least one surface of the film, and the number average particle diameter of 0 is formed on the surface of particles (a). A laminated film having particles (b) of 1 μm or more and 1 μm or less adhered thereto.
(2) A coating layer containing particles (a) having a number average particle size of 4 μm or more made of resin (A) is provided on at least one surface of the white film, and the number average particle size is formed on the surfaces of the particles (a). The laminated film according to the above, wherein particles (b) having a particle size of 0.1 μm or more and 1 μm or less are adhered.
(3) The laminated film according to (1), wherein the film is transparent, and the total light transmittance of the film is 60% or more.
(4) The laminated film according to (1) or (3), wherein an average of 10 or more particles (b) are adhered to the surface of one particle (a).
(5) The laminated film according to any one of (1) to (4), wherein the particles (a) are made of a polyester resin.
(6) The laminated film according to any one of (1) to (5), wherein the particles (b) are made of a resin (B) different from the resin (A).
(7) The laminated film according to any one of (1) to (5), wherein the particles (b) are inorganic particles.
(8) The laminated film according to any one of (1) to (7), wherein the thickness of the coating layer is less than 1 μm.
(9) The laminated film according to any one of (1) to (7), wherein the thickness of the coating layer is less than 0.5 μm.
(10) The laminated film according to any one of (1) to (9), wherein the number average particle diameter of the particles (a) is 4 μm or more and 60 μm or less.
(11) The laminated film according to any one of (1) to (10), wherein the number average particle size of the particles (b) is from 100 nm to 800 nm.
(12) The laminated film according to any one of (1), (2), and (4) to (11), which is a reflector for an edge type backlight unit.
(13) An edge type backlight unit using the laminated film according to any one of (1) to (11).

According to the laminated film of the present invention, the (1) the light guide plate, the reflective plate, and the optical sheet are non-uniformly adhered to each other and the luminance unevenness is generated, and (2) the light guide plate and the reflective plate. And the optical sheet is in close contact, and the light expansion and contraction of the light guide plate causes wrinkles on the reflection plate and the optical sheet, resulting in uneven brightness. (3) The light guide plate surface is scratched and / or the reflection plate surface The beads of the optical sheet are scraped off, and the problem of causing uneven brightness can be prevented.

It is a scanning electron microscope (SEM) photograph of the particle | grains of the laminated | multilayer film surface.

In the laminated film of the present invention, a coating layer containing particles (a) having a number average particle diameter of 4 μm or more made of resin (A) is provided on at least one surface of the film, and the number of particles (a) is several on the surface of particles (a). The laminated film is characterized in that particles (b) having an average particle diameter of 0.1 μm or more and 1 μm or less are adhered.

(1.1) Coating layer of laminated film The particles to be included in the coating layer of the present invention are composed of particles (a) to which particles (b) are attached. By attaching the particle (b) having a small particle size to the surface of the particle (a), the light guide plate is not thermally expanded and contracted to cause wrinkles on the reflecting plate or the optical sheet, thereby preventing uneven brightness. Further, the surface of the light guide plate is not damaged by rubbing the light guide plate and the reflection plate or the optical sheet, and / or the beads on the surface of the reflection plate or the optical sheet are scraped off. Details of the mechanism having these effects are unknown, but when the light guide plate and the reflecting plate or the optical sheet are pressure-bonded and a shearing force is applied, a particle (b) having a small particle diameter is provided on the surface of the particle (a). This is considered to be because the frictional stress decreases, the particles (a) do not stick to the light guide plate, and a large frictional force does not occur between the light guide plate and the reflecting plate or the optical sheet.

As a method for attaching the particle (b) to the surface of the particle (a), for example, a method using the heteroaggregation method described in “Elucidation of dispersion / aggregation and applied technology” issued by Techno System Co., Ltd. can be preferably exemplified. . Specifically, when inorganic particles and / or organic particles exemplified in SiO ₂ whose ζ potential varies depending on pH are contained in the coating liquid, the pH of the coating liquid is adjusted to adjust the ζ potential of the inorganic particles and / or organic particles. There is a method in which the pH is adjusted so that the signs are different, and small particles are attached around the large particles. In this case, there are many cases where the pH range is extremely limited depending on the particle diameter and surface condition of the particles, and depending on the combination of organic particles and inorganic particles, there may be no condition for heteroaggregation. Preferred inorganic materials include metal oxides such as SiO ₂ , TiO ₂ , γ-Al ₂ O ₃ and ZnO. In the case of a combination of organic particles and organic particles, both ζ potentials often have the same sign, and in order to hetero-aggregate, the particle size is as described in “Recent Chemical Engineering Special Powder Technology” edited by the Chemical Industry Association. Heteroaggregates can be obtained by increasing the difference in the surface potential of the particles. In particular, the difference in ζ potential between the particles (a) and the particles (b) is preferably 20 mV or more, more preferably 30 mV or more, and further preferably 40 mV or more. The ζ potential of each particle is preferably a combination in which the particle (a) is from −30 mV to −20 mV and the ζ potential of the particle (b) is from −120 mV to 60 mV. As a method for setting the ζ potential of the particles in the above range, there are cases where it can be achieved by adjusting the amounts of terminal COOH groups, phenolic OH groups and terminal NH ₂ groups of the resin constituting the particles. Specifically, the negative ζ potential may be increased by the presence of these end groups on the surface of the particle. An anionic surfactant may be used. As a method for reducing the potential, the ζ potential difference may be reduced by adsorbing organic ions or complex ions by adsorption, adsorbing a cationic surfactant, or forming a salt.

The number of particles (b) adhering to the surface per particle (a) is preferably 10 or more on average. More preferably, it is 50 or more, and most preferably 100 or more. By having 10 or more, the contact area of a light-guide plate and particle | grains (a) falls, and it can reduce a damage. The upper limit is estimated to be 500 or less. An excessively large particle coverage on the surface is not preferable because it becomes the same as a giant particle consisting of only the particles (b) and eventually sticks to the light guide plate and causes scratches and drops. In order to set the number of particles (b) adhering to the surface per particle (a) to 10 or more, for example, by setting the difference in ζ potential between particles (a) and particles (b) to 20 mV or more. Can be adjusted. Moreover, in order to make it 500 or less, it can adjust by adjusting the compounding quantity of particle | grains (b). The number of attached particles in the present invention refers to the number of particles (b) attached to the surface of one particle (a) when the surface is observed with an SEM.

(1.2) Particle (a)
Particle (a) consists of resin (A). The type of the resin (A) is not particularly limited, but a polymethacrylic acid methyl acrylate resin, an acrylic styrene resin, a polymethyl methacrylate resin, a polybutyl methacrylate resin, a silicone resin, a polystyrene resin, a polycarbonate resin, a benzoguanamine resin, Examples include melamine resins, polyolefin resins, polyester resins, polyamide resins, polyimide resins, or polyfluorinated ethylene resins, and cross-linked products thereof.

In the present invention, an acrylic resin, a nylon resin, and a polyester resin are particularly preferable from the viewpoint of easily controlling the elasticity of the resin and having good affinity with the binder.

Particularly preferred is a thermoplastic polyester resin. Preferred polyesters are aromatic polyesters and polyester elastomers such as polyethylene terephthalate and polybutylene terephthalate because the elasticity of the resin can be easily controlled. Specific examples of the polyester elastomer include various trade names such as “HYTREL” (registered trademark) manufactured by DuPont, “RITEFLEX” (registered trademark) manufactured by Ticona, and DSM. There are “ARNITEL” (registered trademark) manufactured by the company and sold by many companies.

The resin (A) constituting the particles (a) preferably has a flexural modulus of 500 MPa to 3000 MPa. More preferably, it is 1000 MPa or more and 2700 MPa or less. The flexural modulus in the present invention refers to a value measured according to ASTM-D790-98. For the measurement at this time, the resin (A) was dried with hot air at 90 ° C. for 3 hours or more, and the dried pellets were used with an injection molding machine (Nissei Resin Kogyo NEX-1000) with a cylinder temperature of 240 ° C. and a mold. A 127 × 12.7 × 6.4 mm bending test specimen obtained by molding under molding conditions of a temperature of 50 ° C. is used as a measurement sample. If the flexural modulus is smaller than the above range, white spots may occur when applied on a white film and incorporated in a liquid crystal display as a reflector. If the flexural modulus is larger than the above range, the light guide plate may be damaged when the light guide plate and the reflective plate are rubbed together. In order to adjust the flexural modulus of the thermoplastic resin within the above range, for example, a long-chain polyalkylene glycol is copolymerized with an aromatic polyester. In addition, in the case of “HYTREL” (registered trademark) manufactured by DuPont, Hytrel 7247 and Hytrel 8238 have a bending elastic modulus within the above range, and can be used.

As a method for producing the particles (a), a method of obtaining spherical particles by spraying from a nozzle after heating and melting (Japanese Patent Publication No. 2-12975), cooling and precipitating after dissolving in a heating solvent. A method for obtaining spherical particles (Japanese Patent Laid-Open No. 51-79158), and a method for obtaining spherical particles by forcibly dispersing a heat-melted resin in an incompatible heated polysiloxane (Japanese Patent Laid-Open No. 2001-213970). ), A method in which a polymer solution is phase-separated, an emulsion is formed, and fine particles are obtained by adding a poor solvent (International Publication No. 2009/142231). From the viewpoint of easily controlling the particle size, making it easy to reduce the particle size distribution index, and less likely to cause yellowing of the particles due to thermal degradation due to melting, the polymer solution is phase-separated to form an emulsion, A method of obtaining fine particles by adding a poor solvent is preferably used.

The number average particle diameter of the particles (a) is 4 μm or more, preferably 6 μm or more, and more preferably 8 μm or more. The upper limit is preferably 60 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. If it is less than 4 μm, white spots may occur when it is applied on a reflective film and incorporated in a liquid crystal display, and if it is greater than 60 μm, particles may fall off. As a method of adjusting the particle diameter within the above range, a known method can be used. Specific examples include the methods described in JP-A No. 2001-213970 and International Publication No. 2009/142231.

The particles (a) made of the resin (A) of the present invention preferably have a particle size distribution index of 1 to 3. More preferably, it is 1 to 2, and most preferably 1 to 1.5. When the particle size distribution index is within the above range, only a part of the particles having a large particle size are in close contact with the light guide plate and deformed when the reflector is pressed against the light guide plate. It can be prevented from becoming easy. In addition, when the particle size distribution index is larger than the above range (that is, when coarse particles are included), there is a case where, for example, a Mayer bar particle clogging described later occurs in the coating process, and coating stripes may be generated. May be undesirable. As a method for setting the particle size distribution index in the above range, in the method of forming an emulsion by phase-separating a polymer, it is preferable that the temperature for carrying out the emulsion formation and the micronization step is 100 ° C. or higher. The upper limit is the temperature at which dissolution and phase separation occur, and there is no particular limitation as long as the desired fine particles can be obtained, but it is usually in the range of 100 ° C. to 300 ° C., preferably 100 ° C. to 280 ° C., More preferably, it is 120 ° C. to 260 ° C., further preferably 120 ° C. to 240 ° C., particularly preferably 120 ° C. to 220 ° C., and most preferably in the range of 120 ° C. to 200 ° C.

The particle size distribution index referred to in the present invention means a value obtained by dividing the volume average particle size (Dv) of the particles (a) by the number average particle size (Dn).

(1.3) Particle (b)
The particles (b) are preferably made of a resin (B) different from the resin (A) constituting the particles (a). If the resin (B) is the same as the resin (A), the particle (b) may not adhere to the surface of the particle (a). The type of the resin (B) is not particularly limited as long as it is a combination different from the resin (A), but polymethacrylic acid methyl acrylate resin, acrylic styrene resin, polymethyl methacrylate resin, polybutyl methacrylate resin, silicone resin, polystyrene Resin, polycarbonate resin, benzoguanamine resin, melamine resin, polyolefin resin, polyester resin, polyamide resin, polyimide resin, polyfluoroethylene resin, and cross-linked products thereof.

In the present invention, it is preferable to select a resin having a change in ζ potential different from that of the particles (a) depending on the pH of the coating solution. When the resin (A) is a polyester resin, a polystyrene resin or a nylon resin can be preferably selected as the resin (B).

The particles (b) may be inorganic particles. The inorganic particles are preferably used in many cases because the particles (b) can be attached to the surfaces of the particles (a) by adjusting the pH of the coating solution. The type of inorganic particles is not limited, but metal oxides are preferably used because they are easily controlled by the pH of the ζ potential. Specific examples of inorganic particles include silica particles, aluminum oxide, titanium dioxide and the like.

The number average particle diameter of the particles (b) is from 0.1 μm to 1 μm, preferably from 100 nm to 800 nm, and most preferably from 200 nm to 500 nm. If it exceeds 1 μm, it may not adhere to the surface of the particles (a), which is not preferable. Further, if it is less than 100 nm, it may be smaller than the thickness of the coating film present on the surface of the particle (a), and it may not be possible to form protrusions on the surface of the particle (a). Specific examples of organic particles having a number average particle size in the above range include various products such as true spherical polystyrene latex particles “DYNOSPHERES” manufactured by Soken Chemical Co., Ltd., cross-linked polymethyl methacrylate particles “Eposter (registered)” manufactured by Nippon Shokubai Co., Ltd. Trademark) MX ", acrylic submicron fine particles" Techpolymer (registered trademark) "manufactured by Sekisui Plastics Co., Ltd., etc., which are sold by many companies and can be used. Specific examples of the inorganic particles include silica particles “Spherica Slurry” manufactured by Catalytic Chemical Industry Co., Ltd. and silica particles “Sea Hoster (registered trademark)” manufactured by Nippon Shokubai Co., Ltd., and these can be used.

(1.4) Binder resin The binder resin is preferably made of a water-soluble resin, and is preferably applied using a water-based coating liquid because it has little influence on the environment. The water-soluble resin as used herein refers to a resin containing at least one functional group selected from sulfonic acid groups, carboxylic acid groups, hydroxyl groups, and salts thereof. The water-soluble resin is preferably a resin in which a monomer having a functional group such as a sulfonic acid group, a sulfonic acid group, a carboxylic acid group, or a carboxylic acid group is copolymerized, and more preferably a carboxylic acid group and / or a carboxylic acid group. A resin in which a monomer having a salt is copolymerized. By being water-soluble, it is possible to form a coating layer having good affinity with the base film and the particles (a) and less dropping of the organic particles (a). In addition, since the binder resin is a water-soluble resin, it can be used in the state of a coating solution in which the binder resin and particles are dissolved or dispersed in water. Of course, a binder resin and particles previously dissolved or dispersed separately in water may be arbitrarily mixed and used. In addition, the use of a coating solution using water enables application in an in-line coating method, which is preferable from the viewpoint of cost saving. As a method of copolymerizing the monomer having the above functional group with the binder resin, a known method can be used. The water-soluble resin is preferably formed from at least one selected from the group consisting of a polyester resin, an acrylic resin, and a polyurethane resin, and more preferably a polyester resin or an acrylic resin. The binder resin has good adhesion to the base film and is preferably transparent, and the resin can satisfy these characteristics. As these water-soluble resins, the product name “Watersol” (registered trademark) manufactured by DIC Corporation, “Pesresin” manufactured by Takamatsu Yushi Co., Ltd., and the like are available.

Further, various additives can be added to the binder resin forming the coating layer as long as the effects of the invention are not impaired. As the additive, for example, an antioxidant, a crosslinking agent, a fluorescent brightening agent, an antistatic agent, a coupling agent and the like can be used.

For example, by adding a crosslinking agent to the coating layer, the adhesion to the base film can be further improved, and at the same time, the organic particles can be further prevented from falling off. Examples of the crosslinking agent include an isocyanate crosslinking agent, a silicone crosslinking agent, and a polyolefin crosslinking agent. The content of the crosslinking agent in the coating layer is preferably 5% by weight or less, more preferably 0.1 to 4% by weight, and further within the range of 0.5 to 3% by weight. Most preferably it is. If the content of the crosslinking agent is within such a preferable range, the effect can be sufficiently obtained, and the film can be prevented from curling after the coating layer is provided.

Further, by adding an antistatic agent, it is possible to prevent foreign matters such as dust from adhering to the film. Examples of the antistatic agent include, but are not limited to, a surfactant, an ionic conductive polymer, an electron conductive polymer, a conductive metal oxide, and metals. Specific examples of the surfactant and the ionic conductive polymer include the following.

Surfactants include cationic surfactants such as sulfonated compounds, N-acyl amino acids or salts thereof, anionic surfactants such as alkyl ether carboxylates, aliphatic amine salts, and aliphatic quaternary ammonium salts. , Amphoteric surfactants such as carboxybetaine, imidazolinium betaine, and aminocarboxylate. Among them, sulfonated compounds are preferably applied, specifically sodium dodecylbenzenesulfonate, sodium stearylbenzenesulfonate, sodium octylbenzenesulfonate, potassium dodecylbenzenesulfonate, lithium dodecylbenzenesulfonate, lithium octylnaphthalenesulfonate, Sodium oxylnaphthalene sulfonate, sodium dodecyl naphthalene sulfonate, potassium dodecyl naphthalene sulfonate, sodium butyl sulfonate, sodium pentyl sulfonate, sodium hexyl sulfonate, sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, decyl sulfone Acid sodium, sodium undecyl sulfonate, sodium dodecyl sulfonate, Sodium Ridecyl sulfonate, Sodium tetradecyl sulfonate, Sodium tetradecyl sulfonate, Sodium pentadecyl sulfonate, Sodium hexadecyl sulfonate, Sodium heptadecyl sulfonate, Sodium octadecyl sulfonate, Potassium decyl sulfonate, Potassium dodecyl sulfonate In addition, potassium octadecyl sulfonate is applicable.

Examples of the ionic conductive polymer include polystyrene sulfonates and their low molecular weight compounds represented by polystyrene sulfonates such as alkali metal salts and ammonium salts thereof, alkyl phosphate ester salts and alkyl ether phosphate ester salts. Examples thereof include a phosphoric acid polymer compound copolymerized as a monomer and a polyacrylic acid ester having an ionic functional group.

The coating thickness of the coating layer (d; the distance from the surface of the base film at the portion not including the particles (a) to the coating layer surface) is preferably less than 1 μm. More preferably, it is less than 500 nm, More preferably, it is less than 400 nm. By setting the coating thickness within the above range, not only the amount of the binder resin used can be reduced, but also the coating by the in-line coating method becomes possible, and the cost can be greatly reduced. Moreover, when the coating thickness is 1 μm or more, the coating appearance such as coating unevenness may be remarkably deteriorated. The lower limit of the coating thickness is preferably 50 nm. If the coating thickness is less than 50 nm, the organic particles may fall off. As a method for measuring the coating thickness of the coating layer, a section including particles is cut, and observed with an SEM or a transmission electron microscope (TEM) to determine the coating thickness of the coating layer. Examples of the method for setting the coating thickness of the coating layer in the above range include a method achieved by adjusting the binder resin concentration of the coating liquid and the coating thickness of the coating liquid.

The surface roughness (SRz; three-dimensional ten-point average roughness) of the coating layer surface is preferably 5 μm or more and 60 μm or less. More preferably, they are 10 micrometers or more and 30 micrometers or less. If the thickness is less than 5 μm, white spots may occur when a laminated film coated on a white film is incorporated as a reflector in a liquid crystal display, and if it is greater than 60 μm, particles may fall off. Examples of the method of adjusting the surface roughness so as to be included in the above range include a method of adjusting the particle size of the organic particles, the binder resin concentration of the coating liquid, and the coating thickness of the coating liquid.

The particles (a) and particles (b) are preferably covered with a binder resin. By covering the particles with the binder resin, it can be made difficult to fall off. The particles can be coated with a binder resin by improving the wettability of the particles by a known method. Moreover, about a coating state, it can confirm by SEM or TEM of a particle cross section. At this time, it can be confirmed more clearly by using ruthenium staining or the like.

The laminated film of the present invention, it is preferred particle density of the organic particles in the coating layer surface is 5 pieces / mm ² or more 100,000 / mm ² or less. More preferably, they are 400 pieces / mm < ² > or more and 100,000 pieces / mm < ² > or less, More preferably, they are 1000 pieces / mm < ² > or more and 100,000 pieces / mm < ² > or less. When a laminated film having a particle density within the above numerical range is used as a reflection plate or a light diffusion film of a liquid crystal display, an appropriate light diffusibility can be obtained. As a method of bringing the particle density of the coating layer surface within the above numerical range, the amount of particles in the coating liquid, the thickness of the coating film, and when coating during film formation, by adjusting the stretching ratio in the stretching step after coating Can be achieved.

In the second aspect of the laminated film of the present invention, a coating layer containing particles (a) having a number average particle size of 4 μm or more made of resin (A) is provided on at least one surface of a white film. It is a laminated film characterized in that particles (b) having a number average particle size of 0.1 μm or more and 1 μm or less are attached to the surface of a), the third aspect is that the film is transparent, and the film Is a laminated film characterized by having a total light transmittance of 60% or more.

The film according to the laminated film of the present invention is a white film or a transparent film.

(2.1) Configuration of white film The white film constituting the laminated film according to the second aspect of the present invention has a high visible light reflectance when used as a backlight for a liquid crystal display or a reflector for lighting applications. Higher is better. The reflectance is preferably 80% or more. More preferably, it is 90% or more, More preferably, it is 95% or more. For this reason, a film containing bubbles and / or incompatible particles therein is preferably used. Although these white films are not limited, white films such as porous unstretched or biaxially stretched polyolefin films and porous unstretched or biaxially stretched polyester films are preferably used. . In particular, a white polyester film is preferably used from the viewpoint of moldability and productivity. The white polyolefin film and the white polyester film are disclosed in JP-A-4-239540, JP-A-8-262208, JP-A-2002-90515, JP-A-2002-138150, and JP-A-2004-330727. The white film currently used is mentioned.

Examples of the plastic resin constituting the white film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and cyclic polyolefin, polystyrene, and acrylic resins. Polyester is preferably used from the viewpoint of moldability and productivity.

Examples of incompatible particles include inorganic particles made of titanium oxide, barium sulfate, silicon dioxide, calcium carbonate, and the like, and organic particles such as acrylic particles, nylon particles, polystyrene particles, and silicone particles. Further, an incompatible resin can be used for the thermoplastic resin constituting the white film, and the incompatible resin can be dispersed in an extruder. Examples of incompatible resins include olefin resins such as polypropylene, polymethylpentene, and cyclic polyolefin, and polystyrene resins when the thermoplastic resin constituting the white film is polyester.

The white film may be a single layer film or a laminated film.

The thickness of the white film is not particularly limited as long as the application to be used is appropriately selected depending on the required properties. For liquid crystal TVs, a thickness of 250 μm or more and 600 μm or less is preferably used from the viewpoint of film rigidity. Moreover, in a liquid crystal monitor use, 188 micrometers or more and 300 micrometers or less are used preferably.

It is preferable that the surface on which the coating layer containing the particles (a) and particles (b) of the laminated film of the present application is provided is the surface in contact with the light guide plate of the white film.

(2.2) Structure of transparent film The transparent film constituting the laminated film of the present invention refers to a film having a total light transmittance of 60% or more. When used as a diffusion sheet in a backlight for liquid crystal display, the total light transmittance is preferably 70% or more, more preferably 90% or more. For this reason, the internal diffusion film which contains an incompatible particle | grain inside, and the diffusion film which provided the diffusion layer containing a bead on the base film surface are used preferably. Examples of the diffusion film having a diffusion layer on the surface include diffusion films disclosed in JP-A-2007-86730.

Examples of the plastic resin constituting the transparent film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and cyclic polyolefin, polystyrene, and acrylic resins. Polyester is preferably used from the viewpoint of moldability and productivity.

The thickness of the transparent film is not particularly limited as long as the application to be used is appropriately selected depending on the required properties. For liquid crystal TVs, from 50 μm to 150 μm is preferably used from the viewpoint of film rigidity. Moreover, in the liquid crystal monitor use, 30 to 100 μm is preferably used.

The surface on which the coating layer containing particles (a) and particles (b) of the laminated film of the present application is provided is preferably the surface in contact with the light guide plate of the transparent film. When the transparent film is a diffusion film, the surface is preferably different from the surface provided with the diffusion layer. When the transparent film is a prism sheet, the surface is preferably different from the prism surface.

(3) Manufacturing method When forming an application layer on at least one surface of the white film, which is the second aspect of the present invention, for example, a mixture containing a polyester resin and an incompatible component is sufficiently vacuumed as necessary. It dries and supplies to the heated extruder of the film forming apparatus which has an extruder (main extruder). The incompatible component may be added using a master chip prepared by melt-kneading and mixing uniformly in advance, or may be directly supplied to a kneading extruder. It is preferable to use a master chip obtained by melt-kneading a mixture containing a polyester resin and an incompatible component uniformly in advance because dispersion of the incompatible component is promoted.

In addition, it is preferable to melt-extrude, after filtering through a filter having a mesh of 40 μm or less, to introduce into a T-die die and obtain a molten sheet by extrusion molding. The molten sheet is closely cooled and solidified by static electricity on a drum cooled to a surface temperature of 10 ° C. or more and 60 ° C. or less to produce an unstretched film.

A laminated film having a coating layer on the surface can be obtained by stretching and heat-treating this unstretched film according to an in-line coating method described later.

Moreover, when forming a coating layer in the at least one surface of the transparent film which is the 3rd aspect of this invention, for example, a polyester resin is fully vacuum-dried as needed, and has an extruder (main extruder). Feed to heated extruder of film forming apparatus.

In the case where a light diffusion layer is provided on one surface of the obtained laminated film, it is preferably formed by dispersing and fixing a large number of organic polymer fine particles with a binder. The organic polymer fine particles are preferably particles made from an organic polymer such as a cross-linked acrylic resin and methacrylic resin, polyethylene, polypropylene, polystyrene, silicone resin, melamine resin, etc., and in particular, a cross-linked acrylic resin or methacrylic resin (PMMA). Resin). The mass average particle diameter of the organic polymer fine particles is preferably 1 to 100 μm, and more preferably 1 to 25 μm. As the binder of the light diffusion layer, an organic polymer binder is preferable, and as the organic polymer binder, for example, a homopolymer or a copolymer containing at least one of acrylic acid ester and methacrylic acid ester as one component of a monomer. (Meth) acrylic resin is particularly preferable. It is preferable to form the coating liquid prepared by adding and mixing the organic polymer binder and the organic polymer fine particles in a suitable solvent, and applying and drying on the laminated film.

The content of the organic polymer fine particles is preferably 100 to 500 parts by mass, more preferably 200 to 400 parts by mass with respect to 100 parts by mass of the binder.

The solvent is preferably an organic solvent having a boiling point of 150 ° C. or less from the viewpoint of easy drying after coating, and cyclohexanone, 1,4-dioxane, and ethylene glycol monomethyl ether acetate are particularly preferable. Other organic solvents such as alcohol may be mixed with the organic solvents listed above, and methyl ethyl ketone is preferably used from the viewpoint of versatility.

Application to the laminated film can be performed using a known application means such as a spin coater, a roll coater, a bar coater, or a curtain coater. The temperature in the drying step is preferably 90 to 130 ° C, more preferably 100 to 120 ° C. The time is preferably 10 seconds to 5 minutes, more preferably 1 to 2 minutes.

In the first, second and third embodiments of the present application, the laminated film is provided with a coating layer containing particles (a) having a number average particle diameter of 4 μm or more made of resin (A). Particles (b) having a number average particle diameter of 0.1 μm or more and 1 μm or less are attached to the surface of a). As a method for forming the coating layer, in addition to the method of applying the coating liquid to the base film after biaxial stretching (offline coating method), the method of stretching and heat-treating the film after applying the coating liquid (inline coating method) There is. From the viewpoint of adhesion between the coating layer and the base film and cost saving, an in-line coating method is preferable. As the in-line coating method, a method in which a coating liquid is applied to the surface of an unstretched film and then stretched in a biaxial direction, or a direction (for example, uniaxial) that intersects the previous uniaxial stretching direction after the coating liquid is applied to a uniaxially stretched film surface Although the method of extending | stretching further in the direction orthogonal to the extending | stretching direction etc. is mentioned, the latter is preferable.

The latter method, in which the coating agent is applied to the surface of the uniaxially stretched film and then further stretched in the direction crossing the previous uniaxially stretched direction, is preferably carried out as follows. First, a thermoplastic resin raw material is supplied to an extrusion device, melt extrusion is performed at a temperature equal to or higher than the melting point of the thermoplastic resin, and extruded as a molten sheet from a slit-shaped die onto a rotating cooling drum, and a glass transition is performed on the surface of the rotating cooling drum. Rapidly solidify to a temperature below the temperature to obtain an unstretched sheet in an amorphous state. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method is preferably employed.

Next, the unstretched sheet is stretched in the longitudinal direction. The stretching temperature is usually in the range of (the glass transition temperature of the thermoplastic resin constituting the base film −5 ° C.) to (the glass transition temperature of the thermoplastic resin constituting the base film + 25 ° C.), and the stretching ratio is usually 3 to 6 Double the range. Stretching can be performed in one step or in two or more steps. Next, a coating solution is applied to at least one surface of the film. As a coating method of the coating liquid, for example, a Mayer bar coater, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or any other coating apparatus can be used. The coating layer may be formed on only one side of the film or on both sides. When formed only on one side, other characteristics can be imparted by forming a coating layer different from the above-mentioned coating layer on the opposite surface as necessary. In addition, in order to improve the applicability | paintability and adhesiveness to the film of a coating liquid, you may give a chemical process and an electrical discharge process to a film before application | coating.

The coated film is preheated to a temperature range of 90 to 150 ° C. in the preheating zone of the tenter and appropriately dried, and then stretched in the width direction (direction perpendicular to the longitudinal direction). The stretching temperature is usually in the range of (the glass transition temperature of the thermoplastic resin constituting the base film −5 ° C.) to (the glass transition temperature of the thermoplastic resin constituting the base film + 40 ° C.), and the stretching ratio is usually The range is 3 to 6 times, preferably 3.2 to 4.5 times. Prior to the preheating, the film may be once cooled below the glass transition point.

Next, heat treatment is performed for 1 second to 5 minutes under 20% elongation, contraction or constant length. At this time, in order to make the heat shrinkage rate in the longitudinal direction and / or the width direction particularly suitable, relaxation treatment is usually performed within 10%, preferably within 5% in the longitudinal direction and / or the width direction during or after the heat treatment step. You may do. The heat treatment temperature varies depending on the stretching conditions, but is usually in the range of 180 to 250 ° C., preferably 190 to 230 ° C. When the heat treatment temperature exceeds 250 ° C., the orientation of the film tends to decrease, and a part of the coating layer may be thermally decomposed. On the other hand, when the heat treatment temperature is lower than 180 ° C., the thermal shrinkage rate of the film may become too large.

Examples of the method for adjusting the coating liquid include a method in which a binder resin and particles are dissolved or dispersed in order in water, and a method in which a binder resin and particles are separately dissolved and dispersed in water in advance. The coating solution contains a binder resin, particles, and water, and it is preferable to adjust the water content to 50% by weight or more with respect to the coating solution in order to reduce coating stripes. *

(4) Measurement / Evaluation Method (4.1) Measurement Method of Surface Roughness (SRz) Measurement was performed according to JIS-B-0601 (2001). As the measuring instrument, a surface roughness meter (model number: SE3500) manufactured by Kosaka Laboratory was used. The measurement conditions are as follows.
・ Feeding speed: 0.1mm / s
・ X pitch: 1.00μm
・ Y pitch: 5.0μm
・ Z measurement magnification: 20000
-Low frequency cut: 0.25 mm.

(4.2) Method for measuring thickness (d) of coating layer and method for evaluating coating state of organic particles in coating film A section of 70 to 100 nm in thickness is cut out with a microtome in the cross-sectional direction, and ruthenium tetroxide is used. Stained. From the cross-sectional photograph taken by magnifying the stained section with a transmission electron microscope “TEM2010” (manufactured by JEOL Ltd.) at a magnification of 500 to 10,000 times, the thickness of the coating layer where there is no organic particle is shown. Measured and determined. Measurement was performed at 10 randomly selected locations, and the average value was taken as the thickness of the coating layer.

Moreover, the coating state in the coating film of an organic particle was confirmed with the obtained cross-sectional photograph, and it determined as follows.
When the coating film covers the entire surface area of the particles: A
When the particle surface area is covered by 80% or more and less than 10%: B
When the particle surface area is more than 40% and less than 80%: C
When the coating of the particle surface area is less than 40%: D.

(4.3) Measuring method of number average particle size R of particle in coating layer, particle size distribution index It was provided on the surface of the laminated film with a scanning electron microscope (JEOL Ltd. scanning electron microscope JSM-6301NF). The particles in the coated layer were observed and the particle size was measured. When the particle was not a perfect circle, the major axis was measured as its particle size. Further, the number average particle diameter R (Dn) and the volume average particle diameter (Dv) were determined from the above particle diameter values measured for 100 randomly selected particles.

The particle size distribution index (PDI) was calculated according to the following formula (1).

PDI = Dv / Dn (1)
Dn: number average particle diameter, Dv: volume average particle diameter, PDI: particle diameter distribution index.

(4.4) Number of particles (b) adhering to particles (a) Coating layer provided on the surface of the laminated film using a scanning electron microscope (JEOL scanning electron microscope JSM-6301NF) The number of particles (b) adhering to the particles (a) was counted. The number of particles (b) adhering to 20 particles (a) was counted, and the average number of particles per particle (a) was taken as the number of particles (b) adhering to particles (a).

(4.5) Display White Point Evaluation Method A laminated film is installed in the backlight unit of an LED display (T240HW01) manufactured by AUO and installed so that the screen is horizontal. The state when the center of the screen was pressed with a predetermined weight was evaluated according to the following criteria. At this time, in the case of a laminated film having a white film as a base material, the measurement was performed as a reflector, and in the case of a laminated film having a transparent film as a base material, measurement was performed between the light guide plate and the optical sheet.

When white spots occur without weight: F
When white spots occur with a weight of 0.5 kg: E
When white spots occur with a weight of 1.0 kg: D
When white spots occur with a weight of 1.5 kg: C
When white spots occur with a weight of 2.0 kg: B
When a white spot does not occur with a weight of 2.0 kg: A
In addition, the used backlight is a side light type backlight, has a light guide plate and a light source (LED), and a light source is located in the edge part of a light guide plate. In this white point evaluation method, it is possible to clearly distinguish between a case where no white point occurs and a case where a white point occurs.

(4.6) Measuring method of particle density of organic particles The surface of the laminated film was observed with a scanning electron microscope (JEM-6301NF, manufactured by JEOL Ltd.), and the number of particles in 10 fields of 250 μm × 400 μm. And the number N was defined as the particle density of the organic particles (pieces / mm ² ). At this time, the number of particles (b) adhering to the particles (a) is not counted.

(4.7) Evaluation of shaving of light guide plate and dropout of particles on reflection film
After laminating a 40-inch liquid crystal television (manufactured by Samsung, PAVV UN40B7000WF) so that the convex portions of the laminated film are in contact with each other, 200 gf / cm ² (0.0196 MPa), 100 gf / cm ² the reflective sheet sample under a load of (0.0098MPa) and 50gf / cm ² (0.0049MPa) pulling at a linear velocity of 1 m / min, the degree of scratches occurring on the surface of the light guide plate with the naked eye It confirmed and evaluated as follows. About the same sample, it implemented by each load 3 times and evaluated visually.
Class A: No scratches are seen under any load.
Class B: 200 gf / cm ² of but scratches is observed under load, under a load of 100 gf / cm ^2, not seen wounds under a load of 50 gf / cm ^2.
Class C: 200gf / cm ^2, but scratches observed under a load of 100 gf / cm ^2, Under a load of 50 gf / cm ^2, scratches can not be seen.
Class D: Scratches are observed under a load of 50 gf / cm ² .
In addition, it was confirmed that the organic particles were removed from the reflective film.
Class A: No dropout of particles is observed under any load.
Class B: 200 gf / cm under ² loads but particle shedding observed, under a load of 100 gf / cm ^2, not seen particles falling in under a load of 50 gf / cm ^2.
Class C: 200gf / cm ^2, but the particle shedding observed under a load of 100 gf / cm ^2, not seen particles falling in under a load of 50 gf / cm ^2.
Class D: Dropping of particles is observed under a load of 50 gf / cm ² .

(4.8) Reflectivity of laminated film A spectrophotometer U-3410 (Hitachi, Ltd.), φ60 integrating sphere 130-0632 (Hitachi, Ltd.) (inner surface made of barium sulfate) and 10 ° tilt spacer The light reflectivity of 560 nm was determined in a state of mounting. In addition, the value which measured and calculated | required the light reflectance from the application surface side of a laminated film was made into the reflectance of the said white film. Part No. 210-0740 (aluminum oxide) manufactured by Hitachi Instrument Service Co., Ltd. was used as the standard white plate. Five samples were measured and the average was taken as the reflectance.

(4.9) Total light transmittance of laminated film It was measured using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS K7361-1997. At that time, the coated surface was placed on the light source side and measured. Five samples were measured, and the average was taken as the total light transmittance.

EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, this invention is not limited to this.
[material]
(1) White film as a base film, resin for transparent film / PET (polyethylene terephthalate) resin Polyester pellets using terephthalic acid as acid component and ethylene glycol as glycol component to obtain antimony trioxide (polymerization catalyst) On the other hand, it was added so as to be 300 ppm in terms of antimony atoms, and a polycondensation reaction was performed to obtain a polyethylene terephthalate pellet (PET) resin having an intrinsic viscosity of 0.63 dl / g. The glass transition temperature of the obtained PET resin was 80 ° C.
Cyclic olefin copolymer resin As an incompatible component, a cyclic olefin resin “TOPAS” (registered trademark, polyplastics) having a glass transition temperature of 178 ° C. and an MVR (260 ° C./2.16 kg) of 4.5 ml / 10 min. Used).

(2) Coating liquid for forming the coating layer / Polyester binder resin (Material A)
Pesresin A-215E (Takamatsu Yushi Co., Ltd., 30 wt% solution) was diluted with purified water to prepare a 25 wt% solution.
・ Surfactant (Material B)
“Novec” (registered trademark) FC-4430 (manufactured by Hishoe Chemical Co., Ltd., 5 wt% solution) was used.
・ Crosslinking agent (Material C)
“Epocross” WS-500 (manufactured by Nippon Shokubai Co., Ltd.)
・ Organic particles (Material D-1)
An aqueous dispersion “DYNOSPHERES” made of Souken Chemical Co., Ltd. with a spherical concentration of 0.05 μm and a solid content concentration of 1% was used.
・ Organic particles (Material D-2)
An aqueous dispersion “DYNOSPHERES” having a solid concentration of 1% made of true spherical polystyrene particles having a particle diameter of 0.3 μm manufactured by Soken Chemical Co., Ltd. was used.
・ Organic particles (Material D-3)
An aqueous dispersion “DYNOSPHERES” having a solid content concentration of 1% of true spherical polystyrene particles having a particle diameter of 0.6 μm manufactured by Soken Chemical Co., Ltd. was used.
・ Organic particles (Material D-4)
An aqueous dispersion “DYNOSPHERES” made of Souken Chemical Co., Ltd. with a spherical particle size of 0.9 μm and a solid content concentration of 1% was used.
・ Organic particles (Material D-5)
An aqueous dispersion “DYNOSPHERES” having a solid concentration of 1% made of true spherical polystyrene particles having a particle diameter of 1.2 μm manufactured by Soken Chemical Co., Ltd. was used.
・ Organic particles (Material D-6)
An aqueous dispersion “DYNOSPHERES” having a solid content concentration of 1% of true spherical polystyrene particles having a particle diameter of 0.2 μm manufactured by Soken Chemical Co., Ltd. was used.
・ Inorganic particles (Material E)
A 10% by weight aqueous dispersion of silica particles having a number average particle size of 0.3 μm mixed with distilled water was used.
・ Organic particles (Material F-1)
Polyetherester (“Hytrel” (registered trademark) 8238, DuPont, weight average molecular weight 27,000, bent) in a 1000 ml pressure glass autoclave (Hyperglaster TEM-V1000N, manufactured by Pressure Glass Industry Co., Ltd.) Elasticity 1100 MPa) 33.25 g, N-methyl-2-pyrrolidone 299.25 g, polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., PVA-1500, weight average molecular weight 29,000: sodium acetate content by washing with methanol) 17.5 g) was added and nitrogen substitution was performed, followed by heating to 180 ° C. and stirring for 4 hours until the polymer was dissolved. Thereafter, 350 g of ion-exchanged water as a poor solvent was dropped at a speed of 2.92 g / min via a liquid feed pump. After the entire amount of water has been added, the temperature is lowered while stirring, and the resulting suspension is filtered, washed with 700 g of ion exchange water and reslurried, and the filtered product is vacuum dried at 80 ° C. for 10 hours. As a result, 28.3 g of a white solid was obtained. When the obtained powder was observed with a scanning electron microscope, it was a spherical fine particle, and polyether ester fine particles having a number average particle size of 12.0 μm, a volume average particle size of 14.7 μm, and a particle size distribution index of 1.23. Met. The melting point of this polyether ester was 224 ° C., and the temperature-falling crystallization temperature of this polyether ester was 161 ° C. The obtained particles were mixed with purified water to prepare a 40% by mass aqueous dispersion, which was designated as material F-1.
・ Organic particles (Material F-2)
Except for adjusting the amount of the polyether ester, polyether ester fine particles having a number average particle diameter of 3.0 μm were obtained under the same conditions as the organic particles (material F). The obtained particles were mixed with purified water to prepare a 40% by mass aqueous dispersion.
・ Organic particles (Material F-3)
Except for adjusting the amount of the polyether ester, polyether ester fine particles having a number average particle diameter of 5.0 μm were obtained under the same conditions as the organic particles (material F). The obtained particles were mixed with purified water to prepare a 40% by mass aqueous dispersion.
・ Organic particles (Material F-4)
Except for adjusting the amount of the polyether ester, polyether ester fine particles having a number average particle diameter of 20.0 μm were obtained under the same conditions as for the organic particles (material F). The obtained particles were mixed with purified water to prepare a 40% by mass aqueous dispersion.

[Example 1]
(1) Preparation of coating liquid The raw materials of the coating liquid were prepared in the order of 1) to 5) for the following materials, and stirred for 10 minutes with a universal stirrer to prepare a coating liquid. The adjusted coating solution was adjusted to pH 6.5 using 0.1 N hydrochloric acid.
1) Purified water: 33.3 parts by weight 2) Material A: 17.1 parts by weight 3) Material B: 0.6 parts by weight 4) Material C: 4.0 parts by weight 5) Material D-2: 30.0 Part by weight 6) Material F: 15.0 parts by weight (2) Film formation A mixture of 80 parts by weight of PET and 20 parts by weight of cyclic olefin copolymer resin was vacuum-dried at 180 ° C. for 3 hours and then supplied to Extruder A. And melt extrusion at a temperature of 280 ° C. Further, 100 parts by weight of PET was vacuum-dried at a temperature of 180 ° C. for 3 hours, then supplied to the extruder B and melt-extruded at a temperature of 280 ° C. The resins from the respective extruders A and B were merged so as to be laminated in the thickness direction in the order of B / A / B, and then introduced into the T die die.

Next, a melt-laminated sheet is formed by extrusion into a sheet form from the inside of the T die die, and the melt-laminated sheet is closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. A film was obtained. At this time, the film surface in contact with the drum was defined as the back surface, and the surface in contact with the air was defined as the “front” surface. Subsequently, the unstretched laminated film is preheated with a roll (preheated roll) group heated to a temperature of 80 ° C., and then stretched 3.5 times using the difference in peripheral speed of the roll in the longitudinal direction, and 25 ° C. A uniaxially stretched film was obtained by cooling with a roll group at a temperature of 5 ° C.

Subsequently, the “front” surface of the uniaxially stretched film was subjected to corona discharge treatment in the air, and the coating layer forming coating solution was applied to the treated surface by a bar coating method using a Mayer bar.

The both ends of the uniaxially stretched film coated with the coating layer forming coating solution are guided to a 100 ° C. preheating zone in the tenter while being held by clips and dried, and then continuously continuous in the heating zone at 100 ° C. in the direction perpendicular to the longitudinal direction. The film was stretched 3.5 times in the direction (lateral direction). Subsequently, after performing a heat treatment at 190 ° C. in the heat treatment zone in the tenter and further performing a relaxation treatment in the transverse direction at 190 ° C. by 6%, the film was then uniformly cooled and wound up, and on a film having a thickness of 188 μm, A white laminated film provided with a coating layer having a thickness of 200 nm was obtained. The film thickness of the B layer was 10 μm. Tables 1 and 2 show the evaluation results of the coating liquid composition and the physical properties of the obtained laminated film.

FIG. 1 shows the result of observing organic particles contained in the coating layer of the laminated film obtained in this example with an SEM. The organic particles (material D) are in a state of adhering to the surface of the organic particles (material F).

[Examples 2 to 11]
Except that the composition of the coating layer-forming coating solution is as shown in Table 1 and the thickness of the coating layer is as shown in Table 2, film formation is performed under the same conditions as in Example 1, and the thickness is 188 μm. A laminated white film was obtained. Various properties of the film are shown in Table 2. In all cases, the coating appearance was good, and there was little dropout of particles.

Example 12
PET was vacuum-dried at a temperature of 180 ° C. for 3 hours, then supplied to the extruder A, and melt-extruded at a temperature of 280 ° C. The molten resin from the extruder A was introduced into the T die die.

Next, a molten PET sheet is formed by extrusion into a sheet from the inside of the T die die, and the molten PET sheet is closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. A film was obtained. At this time, the film surface in contact with the drum was defined as the back surface, and the surface in contact with the air was defined as the “front” surface. Subsequently, the unstretched PET film was preheated with a roll (preheated roll) group heated to a temperature of 80 ° C., and then stretched 3.5 times using the difference in peripheral speed of the roll in the longitudinal direction, and 25 ° C. A uniaxially stretched film was obtained by cooling with a roll group at a temperature of 5 ° C.

Subsequently, the “front” surface of the uniaxially stretched film was subjected to corona discharge treatment in the air, and the coating layer forming coating liquid shown in Table 1 was applied to the treated surface by a bar coating method using a Mayer bar. .

The both ends of the uniaxially stretched film coated with the coating layer forming coating solution are guided to a 100 ° C. preheating zone in the tenter while being held by clips and dried, and then continuously continuous in the heating zone at 100 ° C. in the direction perpendicular to the longitudinal direction. The film was stretched 3.5 times in the direction (lateral direction). Subsequently, after performing a heat treatment at 190 ° C. in the heat treatment zone in the tenter and further performing a relaxation treatment in the transverse direction at 190 ° C. by 6%, the film was then uniformly cooled and wound up, and on a film having a thickness of 188 μm, A laminated film provided with a coating layer having a thickness of 200 nm was obtained. Tables 1 and 2 show the evaluation results of the coating liquid composition and the physical properties of the obtained laminated film.

[Comparative Example 1]
The composition of the coating layer forming coating solution is the same as in Example 1 except that the conditions are as shown in Table 1, the thickness of the coating layer is as shown in Table 2, the pH is not adjusted, and the pH is maintained at 7.9. Film formation was carried out under the conditions described above to obtain a laminated white film having a thickness of 188 μm. The particles (b) did not adhere to the particles (a), and the particles dropped out on the film in the scratch test. Various properties of the film are shown in Table 2. Particles dropped from the film of Comparative Example 1.

[Comparative Examples 2 to 4]
Except that the composition of the coating layer-forming coating solution is as shown in Table 1 and the thickness of the coating layer is as shown in Table 2, film formation is performed under the same conditions as in Example 1, and the thickness is 188 μm. A laminated white film was obtained. Various properties of the film are shown in Table 2. Particles dropped from the film of Comparative Example 1.

The film of the present invention can be suitably used as a light reflecting plate or an optical sheet. In particular, it can be suitably used as a light reflecting plate for a backlight. Among them, it can be suitably used as a light reflecting plate for a sidelight type backlight. Here, the sidelight-type backlight has at least a light source, a light guide plate, and a reflection plate, but may include a housing or the like. The type of the light source is not particularly limited, but a particularly great effect can be obtained when CCFL or LED is used as the light source.

11: Particle 12 adhering to the surface of particle 12: Particle 13: Binder resin

Claims

At least one surface of the film is provided with a coating layer containing particles (a) having a number average particle size of 4 μm or more made of resin (A), and the number average particle size of 0.1 μm or more is formed on the surface of the particles (a). A laminated film having particles (b) of 1 μm or less adhered thereto.
At least one surface of the white film is provided with a coating layer containing particles (a) having a number average particle size of 4 μm or more, which is made of resin (A), and the number average particle size is 0.1 μm on the surface of the particles (a). The laminated film according to claim 1, wherein particles (b) having a particle size of 1 μm or less are adhered thereto.
The laminated film according to claim 1, wherein the film is transparent, and the total light transmittance of the film is 60% or more.
The laminated film according to any one of claims 1 to 3, wherein an average of 10 or more particles (b) are adhered to the surface of one particle (a).
The laminated film according to any one of claims 1 to 4, wherein the particles (a) comprise a polyester resin.
The laminated film according to any one of claims 1 to 4, wherein the particles (b) comprise a resin (B) different from the resin (A).
The laminated film according to any one of claims 1 to 5, wherein the particles (b) are inorganic particles.
The laminated film according to any one of claims 1 to 7, wherein the thickness of the coating layer is less than 1 µm.
The laminated film according to any one of claims 1 to 7, wherein the thickness of the coating layer is less than 0.5 µm.
The laminated film according to any one of claims 1 to 9, wherein the number average particle diameter of the particles (a) is from 4 袖 m to 60 袖 m.
The laminated film according to any one of claims 1 to 10, wherein the number average particle diameter of the particles (b) is from 100 nm to 800 nm.
The laminated film according to any one of claims 1, 2, and 4 to 11, which is a reflector for an edge type backlight unit.
An edge type backlight unit using the laminated film according to any one of claims 1 to 11.