KR20080091128A - Film for surface light source reflection member - Google Patents

Abstract

A film for surface light source reflection member, consisting of a white film and having a difference of glossiness (60°) between one surface and the opposite surface, G, satisfying the relationship G>80. Thus, there is provided a film for surface light source reflection member that facilitates visual discrimination between a surface provided with a functionalized layer and its opposite surface to thereby realize enhancing of the productivity in the process of production of liquid crystal backlight.

Description

Film for surface light source reflection member {FILM FOR SURFACE LIGHT SOURCE REFLECTION MEMBER}

This invention relates to the film for surface light source reflecting members in which one surface and the other surface are easy to distinguish. More preferably, it is related with the film for surface light source reflecting members with little brightness fall with time. Moreover, it is related with the liquid crystal backlight of the direct type | mold system for liquid crystal displays using this film for surface light source reflection members, the liquid crystal backlight of inverse prism system, and the lamp reflector for backlights.

In a liquid crystal display, a backlight (hereinafter referred to as a liquid crystal backlight) for illuminating a liquid crystal cell is used. In liquid crystal monitors, liquid crystal backlights of an edge light type and direct type liquid crystal backlights of a liquid crystal television are employed. As a film for surface light source reflection members (henceforth a reflective film) used for these liquid crystal backlights, the porous white film formed by the bubble is generally used (patent document 1). Moreover, the white film which laminated | stacked the ultraviolet absorbing layer is also proposed in order to prevent the yellow discoloration of the film by the ultraviolet-ray radiated | emitted from a cold cathode tube (patent document 2, 3). Moreover, the white film which controlled the glossiness of both surfaces of a film in order to provide adhesiveness is also proposed (patent document 4).

Patent Document 1: Japanese Patent Application Laid-open No. Hei 8-262208

Patent Document 2: Japanese Patent Application Laid-Open No. 2001-166295

Patent Document 3: Japanese Unexamined Patent Publication No. 2002-90515

Patent Document 4: Japanese Patent Laid-Open No. 2005-125700

The reflective film is often used in conjunction with an aluminum plate or a stainless plate in the liquid crystal backlight manufacturing process. In addition, in a lamp reflector, a metal plate may not be used and it may be used by the reflective film alone. In these manufacturing processes, since the reflective film which provided the layer which provided the function to one side is white on both sides, it is difficult to distinguish the surface on which the function provision layer was formed, and the surface on the opposite side by visual confirmation. Due to the difficulty in identifying these, there is a problem that productivity is reduced due to extra time in the backlight manufacturing process.

In particular, in a reflective film having a resin layer containing a light stabilizer and / or an ultraviolet absorber on one side, a surface on which an resin layer containing a light stabilizer and / or an ultraviolet absorber is mistakenly formed by these problems is placed on an aluminum plate or a stainless plate. I may attach it. If it adheres by mistake, the surface without the resin layer containing a light stabilizer and / or an ultraviolet absorber will be exposed to light of a cold cathode tube, and will deteriorate. As a result, a serious problem arises that the luminance of a product such as a liquid crystal television using the reflective film decreases over time during use.

Moreover, in the liquid crystal backlight of the anti-prism type | mold which is one kind of edge light type backlight, the reflective film with high glossiness is calculated | required because the reflective film with many regular reflection components is preferable for brightness improvement. On the other hand, when assembling a liquid crystal backlight, the case body of a liquid crystal backlight and a reflective film may contact and damage as shown in FIG. Notebooks to which the edge light type backlight is applied are important to be light in weight, and a cavity is also formed in the case body of the liquid crystal backlight to reduce the weight. In edge-lit backlights, damage caused to the reflective film is seen through this cavity. The liquid crystal backlight which shows damage has a problem that a yield falls because the grade as a finished product falls. In particular, the anti-prism type liquid crystal backlight uses a high gloss reflective film, and this problem is remarkable because damage is easily seen.

MEANS TO SOLVE THE PROBLEM This invention employs the following means in order to solve the said subject. That is, the film for surface light source reflection members of this invention is comprised by the white film, The difference (G) of glossiness (60 degree) of one surface and the other surface is (DELTA) G> 80, It is characterized by the above-mentioned.

Moreover, the preferable aspect of the film for surface light source reflecting members of this invention is

(1) having a resin layer on one side of the white film, and the glossiness (60 °) of the other side of the white film is 90% or more,

(2) the resin layer being a resin layer containing an ultraviolet absorber and / or a light stabilizer,

(3) The thermal contraction rate of the film longitudinal direction and the film width direction after heat-processing at 90 degreeC for 30 minutes is -0.1% or more and 0.2% or less,

(4) The white film is composed of a three-layer structure of A layer / B layer / A layer, the B layer is a layer containing microbubbles, and the A layer contains polyester and inorganic particles and / or organic particles. It is a layer, The particle content is 0.5 weight% or less with respect to the total weight of each A layer,

(5) The white film has a three-layer configuration of A layer / B layer / C layer, B layer is a layer containing fine bubbles, and A layer and / or C layer are inorganic particles and / or polyester in polyester. It is a layer containing organic particle | grains, The particle content is 0.5 weight% or less with respect to the total weight of each said layer containing particle | grains.

Moreover, the liquid crystal backlight of the direct type | mold system of this invention, the lamp reflector for liquid crystal backlights, and the liquid crystal backlight of an inverted prism system use the film for surface light source reflection members of the said invention.

(Effects of the Invention)

According to the film for surface light source reflection members of this invention, the surface on which the functional provision layer was easily formed, and the surface on the opposite side can be distinguished easily by visual confirmation, and productivity in a liquid crystal backlight manufacturing process can be improved. In addition, when the resin layer containing the ultraviolet absorber and / or the light stabilizer is formed as a functional imparting layer, the surface on which the resin layer containing the ultraviolet absorber and / or the light stabilizer is formed and the opposite side can be easily identified by visual confirmation. When mounted on the liquid crystal backlight, the resin layer containing the ultraviolet absorber and / or the light stabilizer can be reliably provided toward the cold cathode tube side, so that the decrease in luminance over time can be reduced. Moreover, when it is used for the liquid crystal backlight of an inverted prism system, the damage of the film which arises by contacting the backlight case body and the film for surface light source reflection members at the time of assembly is hard to be outstanding, and the yield as a liquid crystal backlight can be made high.

1 is a direct type liquid crystal backlight using the film for the surface light source reflection member of the present invention

2 is a liquid crystal backlight having an anti-prism method using the film for the surface light source reflecting member of the present invention.

(Explanation of symbols for the main parts of the drawing)

1: diffuser film 2: prism film

3: diffuser plate 4: film for surface light source reflecting member

5: cold cathode tube 6: case

7: Prism LGP 8: Lamp Reflector

The present invention intensively examines the problem that the white film having a layer imparting a function to one side is difficult to identify the surface on which the functional provision layer is formed and the surface on the opposite side by visual confirmation. Thus, as a result of setting the difference (ΔG) of the glossiness (60 °) between one surface of the film for the surface light source reflection member (hereinafter referred to as a reflective film) to ΔG> 80, a functional provision layer was formed. It is easy to identify the face and the face on the opposite side, and it is intended to solve these problems at once.

In this invention, glossiness (60 degree) means the value measured based on JISK7105 (1981 edition) as incident angle and light receiving angle as 60 degrees. Suga Shikenki digital variable glossmeter (UGV-4D) can be used for the measurement.

The difference ΔG between the glossiness (60 °) of one side and the other side of the reflective film of the present invention needs to be larger than 80% in order to enable identification of one side and the other side. . ΔG is preferably 85% or more, and more preferably 90% or more. If (DELTA) G is 80% or less, surface identification will become difficult. The following method is mentioned as a method of making (DELTA) G larger than 80%.

(1) A difference is given to the glossiness of one surface and the other surface of the white film which comprises a reflection film.

(2) A resin layer is formed in one surface of the white film which comprises a reflection film, and the glossiness of the surface is lowered.

Details of these methods will be described later in detail.

As for the white film which consists of a polymer used as a reflecting film of this invention, it is good that the visible light reflectance is high. In order to make visible light reflectance high, it is preferable to use the white film containing a bubble inside. Although it does not specifically limit as a white film containing foam inside, A porous unstretched or a polypropylene film or a polyester film is mentioned preferably as an example. Among these, a polyester film is especially preferable as a white film which concerns on this invention from the point which is excellent in heat resistance and rigidity.

Polyester which comprises the white film which concerns on this invention is a polymer obtained by polycondensation from diol and dicarboxylic acid. Dicarboxylic acid is represented by terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, adipic acid, sebacic acid, and the like. Diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol, and the like. Specifically, for example, polymethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxyl The rate etc. are mentioned. In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferable.

Of course, these polyesters may be homopolyesters or copolyesters. As the copolymerization component, for example, diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfo Dicarboxylic acid components, such as a phthalic acid, are mentioned.

Moreover, well-known various additives may be added in this polyester. As an additive, antioxidant, antistatic agent, etc. are illustrated, for example.

As a polyester used for the white film which concerns on this invention, a polyethylene terephthalate is preferable. Polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

It is preferable that the average reflectance in the wavelength range of 400-700 nm light of the reflective film of this invention is 90% or more in the at least single side | surface of a reflective film. In the present invention, the average reflectance is measured by applying an integrating sphere to a Hitachi High-Technologies Spectrophotometer (U-3310) and setting the standard white plate (aluminum oxide) to 100% over 400 to 700 nm. From the chart obtained, wavelengths are values obtained by reading and reflecting the reflectance at intervals of 5 nm.

In order to make an average reflectance 90% or more, it is important to contain a fine bubble inside a film and to make it white. Since fine bubbles exert light scattering action, the reflectance can be improved. Preferably the average reflectance is 95% or more, more preferably 98% or more. Although there is no upper limit in particular about average reflectance, it is preferable that it is 108% or less. This is because, in order to increase the average reflectance, it is necessary to increase the addition amount of the nucleating agent, and in that case, the film forming property may become unstable.

It is preferable that the white film which concerns on this invention is whitened by containing a fine bubble in a film inside. Formation of fine bubbles is achieved by finely dispersing a high melting point polyester and an incompatible polymer in a film base material, for example, polyester, and stretching it (for example, biaxial stretching). In extending | stretching, a void (bubble) is formed around this incompatible polymer particle, and since this exerts a scattering effect to light, it becomes white and can obtain a high reflectance. Incompatible polymers are, for example, poly-3-methylbutene-1, poly-4-methylpentene-1, polyvinyl-t-butane, 1,4-trans-poly-2,3-dimethylbutadiene, polyvinylcyclo Hexane, polystyrene, polymethylstyrene, polydimethylstyrene, polyfluorostyrene, poly-2-methyl-4-fluorostyrene, polyvinyl-t-butylether, cellulose triacetate, cellulose tripropionate, polyvinyl fluorine It is a polymer with a melting point of 200 ° C. or higher selected from a lide, polychlorotrifluoroethylene and the like. Among them, polyolefins, particularly polymethylpentene, are preferred for the polyester base material.

As addition amount of incompatible polymer (for example, polyolefin), when the whole layer containing incompatible polymer is 100 weight%, it is preferable that they are 5 weight% or more and 25 weight% or less. If it is less than 5 weight%, the effect of whitening becomes small and it becomes difficult to obtain a high reflectance. When it exceeds 25 weight%, there exists a possibility that mechanical characteristics, such as the intensity | strength of the film itself, may become too low.

This incompatible polymer is more preferably dispersed uniformly. By uniformly dispersing the incompatible polymer, bubbles are uniformly formed in the film, and the degree of whitening, and thus the reflectance, becomes uniform. In order to uniformly disperse the incompatible polymer, it is effective to add a low specific gravity agent as a dispersing aid. A low specific gravity agent is a compound which has an effect which makes specific gravity small, and the effect is confirmed by a specific compound. For example, about polyester, polyalkylene glycol, such as polyethyleneglycol, methoxy polyethyleneglycol, polytetramethylene glycol, polypropylene glycol, an ethylene oxide / propylene oxide copolymer, sodium dodecylbenzenesulfonate, alkylsulfonate Sodium salt, glycerin monostearate, tetrabutylphosphonium paraaminobenzenesulfonate, and the like.

In the case of the white film according to the present invention, as the low specific gravity agent, polyalkylene glycol is particularly preferable, among which polyethylene glycol is preferable. In addition, a copolymer of polybutylene terephthalate and polytetramethylene glycol is also preferably used to improve the dispersibility of the incompatible polymer. As an addition amount of a low specific gravity agent, 10 weight% or more and 25 weight% or less are preferable for the whole layer containing an incompatible polymer as 100 weight%. If it is less than 10 weight%, the effect of addition becomes less. When it exceeds 25 weight%, there exists a possibility that the original characteristic of a film base material may be impaired. Such a low specific gravity agent can be previously added to a film base material polymer, and can be adjusted as a master polymer (master chip).

As described above, the apparent specific gravity of the polyester film is lower than that of the normal polyester film because the white polyester film contains fine bubbles. The addition of a low specific gravity agent lowers the specific gravity. That is, a white and light film is obtained. In order to make this white polyester film lightweight while maintaining the mechanical characteristics as a reflective film, it is preferable that an external specific gravity is 0.5 or more and 1.2 or less. Moreover, since higher reflectance can also be obtained by making an apparent specific gravity into 0.5 or more and 1.2 or less, it is preferable. The apparent specific gravity is more preferably 0.5 or more and 1.0 or less, and particularly preferably 0.5 or more and 0.8 or less.

In order to reduce the apparent specific gravity to 0.5 or more and 1.2 or less, for example, when polymethylpentene having a specific gravity of 0.83 is used as the incompatible polymer, first, polymethylpentene is 5% by weight to 25% by weight with respect to the polyester polymer of the film base material. It is contained in% or less. Subsequently, it can achieve by making a polyester unstretched film and extending | stretching the polyester unstretched film to 2.5-4.5 times in both a longitudinal direction and a lateral direction. When the apparent specific gravity is in the range of 0.5 or more and 1.2 or less, when used as a reflecting film, it exhibits remarkably excellent brightness in brightness of the screen.

The glossiness of the white film according to the present invention is not particularly limited as long as the difference (ΔG) between the glossiness (60 °) of one side and the other side of the reflective film using the white film is greater than 80%, but at least the It is preferable that glossiness (60 degrees) of one surface is 90% or more. If the glossiness of one side of the white film is 90% or more, it is easy to reduce the glossiness of the other side of the white film or to form a resin layer on the other side of the white film to reduce the glossiness of the surface. ΔG of the reflective film can be made larger than 80%. The glossiness of one surface of the white film is more preferably 95% or more, next preferably 100% or more, next preferably 115% or more, and most preferably 120% or more. The upper limit of glossiness is not particularly limited but is preferably less than 130%. When exceeding 130%, since the film surface friction coefficient becomes high, air removal at the time of winding may become difficult.

The white film which concerns on this invention can be formed by various laminated constitutions, such as a single | mono layer, two layers, and three layers. Among them, it is composed of three layers of A layer / B layer / A layer or A layer / B layer / C layer, and the layer B contains the micro-bubbles to achieve high reflectance and film forming property. desirable.

Moreover, various additives can be added to each layer of the said white film in the range which does not impair the effect of this invention. As the additive, for example, organic and / or inorganic fine particles, fluorescent brighteners, heat stabilizers, ultraviolet absorbers, antioxidants and the like can be used, and these may be changed by the difference in glossiness between one side of the reflective film and the other side. It is possible to identify which side of the white film a layer containing an additive having functionality is formed on. In the case of a three-layer structure of A layer / B layer / A layer, the A layer corresponding to the film surface contained the inorganic particles and / or organic particles in the polyester in an amount of 0.5% by weight or less based on the total weight of each A layer. It is preferable that it is a layer. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. In addition, in the case of the three-layer structure of A layer / B layer / C layer, the A layer and / or C layer corresponding to the film surface have each of inorganic layers and / or organic particles in polyester. It is preferable that it is a layer containing 0.5 weight% or less with respect to the total weight of the layer containing particle | grains. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. The glossiness of A layer (or C layer) can be increased by reducing content of the inorganic fine particle and / or organic fine particle contained in A layer (or C layer).

As described above, the white film according to the present invention preferably has a glossiness of at least one surface of 90% or more, but the content of the inorganic fine particles and / or the inorganic fine particles contained in the layer of one outermost surface of the white film is 0.5% by weight. By setting it as%, the glossiness of the surface can be made 90% or more. Moreover, the glossiness of the surface can be lowered by increasing the content of the inorganic fine particles and / or the inorganic fine particles contained in the layer on the other outermost surface of the white film, and the glossiness in one side and the other side of the white film You can pay for tea. The content of the inorganic fine particles and / or the inorganic fine particles contained in each layer can be appropriately adjusted according to the desired glossiness difference.

Next, although the manufacturing method of the white film which concerns on this invention is demonstrated, it is not limited to this example.

Polymethylpentene as an incompatible polymer and polyethyleneglycol, polybutylene terephthalate and polytetramethylene glycol copolymer as low specific gravity agents are added to polyethylene terephthalate. It is sufficiently mixed and dried and fed to an extruder B heated to a temperature of 270 to 300 ° C. If necessary, polyethylene terephthalate containing an inorganic additive such as SiO ₂ is supplied to the extruder A by the conventional method. Then, the three layers of the constitution of A layer / B layer / A layer are made so that the polymer of the extruder B is in the inner layer (B layer) and the polymer of the extruder A is in both the surface layer (A layer) in the T die three-layer detention. You may laminate.

The molten sheet is tightly cooled and solidified by an electrostatic force on a drum cooled to a drum surface temperature of 10 to 60 ° C to obtain an unstretched film. This unstretched film is introduce | transduced into the roll group heated at 80-120 degreeC, it extends 2.0-5.0 times longitudinally in the longitudinal direction, and cools in the roll group of 20-50 degreeC. Subsequently, both ends of the longitudinally stretched film are introduced into the tenter while being gripped by the clip and laterally stretched in the direction perpendicular to the length in an atmosphere heated at 90 to 140 ° C. Although the draw ratio stretches 2.5-4.5 times in length and width, respectively, it is preferable that the area magnification (longitudinal draw ratio X transverse draw ratio) is 9-16 times. If the area magnification is less than 9 times, the white part of the film obtained will be defective. When the area magnification exceeds 16 times, tearing tends to occur during stretching, and the film forming property tends to be poor. In order to impart planarity and dimensional stability to the biaxially stretched film in this way, heat setting of 150-230 degreeC is performed in a tenter, and it is cooled slowly to room temperature after uniformly cooling. And it winds up by a winder and obtains the white film which concerns on this invention.

It is also preferable to form a resin layer on one side of the white film in order to make the difference (ΔG) between the glossiness (60 °) of one side and the other side of the reflective film of the present invention larger than 80%. By forming a resin layer, the glossiness of one surface of a white film can be lowered, and (DELTA) G of a reflective film can be easily made larger than 80%.

Although it does not specifically limit as a resin layer which concerns on this invention, Resin mainly having an organic component is preferable, For example, Polyester resin, a polyurethane resin, an acrylic resin, methacryl resin, a polyamide resin, a polyethylene resin, a polypropylene Resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, fluorine resin and the like. These resins may be used alone or in combination of two or more kinds of copolymers or mixtures. Especially, polyester resin, acrylic, or methacryl resin is used preferably from the point of heat resistance, particle dispersibility, applicability | paintability, and glossiness.

Since the white film of this invention may be deteriorated by the light emitted from lamps, such as a cold cathode tube, especially ultraviolet rays during use (e.g., optical degradation, such as yellowing, or degradation degradation which becomes low molecular weight), a ultraviolet absorber as a resin layer And / or it is also preferable to use the resin layer containing a light stabilizer.

Although it does not specifically limit as resin which comprises the resin layer containing a ultraviolet absorber, resin containing inorganic ultraviolet absorbers, such as titanium oxide and zinc oxide, resin containing organic ultraviolet absorbers, such as benzotriazole and benzophenone, or benzotriazole type And resins obtained by copolymerizing benzophenone-based reactive monomers can be used.

It is preferable to use organic ultraviolet absorbing resin containing resin etc. which copolymerized a hindered amine (HALS) type | system | group reactive monomer as resin which comprises the resin layer containing a light stabilizer.

As an inorganic ultraviolet absorber, zinc oxide, titanium oxide, cerium oxide, zirconium oxide, etc. are common. Among these, at least one selected from the group consisting of zinc oxide, titanium oxide and cerium oxide is preferably used from the viewpoint of not bleeding out and excellent light resistance. Such a ultraviolet absorber may be used together several types as needed. Among them, zinc oxide is most preferable in view of economic efficiency, ultraviolet absorbency and photocatalytic activity. As zinc oxide, FINEX-25LP, FINEX-50LP (made by Sakai Chemical Co., Ltd.), etc. can be used.

Examples of the organic ultraviolet absorbent include resins containing organic ultraviolet absorbents such as benzotriazole and benzophenone or resins obtained by copolymerizing a benzotriazole-based and benzophenone-based reactive monomers, and light stabilizers such as hindered amine (HALS) -based reactive monomers. Further copolymerized resins can be used. In particular, the organic ultraviolet absorbing resin containing a resin copolymerized with a benzotriazole-based or a benzophenone-based reactive monomer, a resin further copolymerized with a hindered amine (HALS) -based reactive monomer, etc. is a thin layer, and has a high ultraviolet absorbing effect, which is more preferable. Do.

These manufacturing methods are disclosed in detail in [0019]-[0039] of Japanese Patent Laid-Open No. 2002-90515. Especially, the Harus hybrid (trademark) {Nippon Shokubai Co., Ltd.} etc. which contain the copolymer of an acryl monomer and a ultraviolet absorber as an active ingredient can be used.

In this invention, various additives can be added to a resin layer in the range which does not impair the effect of this invention. As the additive, organic and / or inorganic fine particles, fluorescent brighteners, crosslinking agents, heat stabilizers, oxidation stabilizers, organic lubricants, nucleating agents, coupling agents and the like can be used.

The resin layer which concerns on this invention can be formed by a coating method. When formed by the coating method, the coating liquid can be applied by any method. For example, methods such as a gravure coat, roll coat, spin coat, reverse coat, bar coat, screen coat, blade coat, air knife coat, dipping and the like can be used. In addition, the coating liquid for formation of a resin layer may be apply | coated (inline coating) at the time of manufacture of the white film of a base material, or may be applied (offline coating) on the white film after completion of crystal orientation.

As for the reflective film of this invention, it is preferable that the thermal contraction rate of the film longitudinal direction and the film width direction after heat processing at 90 degreeC as a reflective film for 30 minutes is -0.1% or more and 0.2% or less. Preferably it is -0.05 to 0.15% or less. When the thermal contraction rate in the film longitudinal direction or the film width direction is out of the range of -0.1% or more and 0.2% or less, the film is warped when high temperature is reached, and the luminance unevenness in the liquid crystal backlight is easily generated. In particular, in the reflective film for inverse prism use, when a prism-shaped light guide plate contacts a mirror-shaped reflective surface, it becomes a screen unevenness on a liquid crystal panel, and it is easy to appear remarkably.

Here, the thermal contraction rate in the film longitudinal direction after heat-processing at 90 degreeC for 30 minutes is the value measured by the following procedures. First, a film sample of a constant size is prepared, and a constant length (L ₀ ) is measured in the longitudinal direction (the extrusion direction at the time of manufacture) at room temperature. The sample is left to stand in a thermostat maintained at 90 ° C. for 30 minutes, and after slow cooling to the same room temperature, the length L of the portion corresponding to L ₀ is measured. Then, the length (L) to the initial length (L ₀₎ the following expression heat shrinkage rate of the calculated value of the film length direction from the.

Thermal contraction rate (%) = {(L ₀ -L) / L ₀ } × 100

Also, negative values indicate that the film is stretched.

In addition, the width direction thermal contraction rate of the film after heat processing at 90 degreeC for 30 minutes means the value measured similarly to the longitudinal direction of a film in the width direction (perpendicular direction with respect to the extrusion direction at the time of manufacture) of a film.

It is preferable that the reflectance film of this invention is 85% or more in average reflectance in the wavelength of 400-700 nm measured from the surface in which the resin layer was formed. More preferably, it is 87% or more, Especially preferably, it is 90% or more. When the average reflectance is less than 85%, the luminance may be insufficient depending on the liquid crystal display to be applied. Moreover, when the resin layer containing a ultraviolet absorber and / or a light stabilizer is formed in both surfaces of a white film, the average reflectance measured from any one resin layer should just be 85% or more.

The reflective film of this invention can be used suitably for the liquid crystal backlight of the direct type | mold system for liquid crystal TV and large-sized monitor use. In the direct type type liquid crystal backlight, as shown in FIG. 1, a reflective film is provided in the vicinity of a cold cathode tube. At this time, unless the surface on which the resin layer of the reflective film (preferably the resin layer containing the ultraviolet absorber and / or the light stabilizer) is provided is directed toward the cold cathode tube side, the white film of the substrate is exposed by the ultraviolet rays emitted from the cold cathode tube. It may turn yellow. Therefore, it is necessary to identify the surface on which the resin layer of the reflective film was formed and the surface on the opposite side at the time of assembling the backlight. In the reflective film of the present invention, the surface on which the resin layer is formed and the surface on the opposite side can be easily identified, and the work efficiency in the backlight assembly process is improved, and the productivity is also improved.

The reflective film of this invention can be used suitably for the lamp reflector of a liquid crystal backlight. The lamp reflector attaches a stainless plate or the like and a reflective film, and is press-molded in a curved shape so that the reflective film is inward. As shown in Fig. 2, the lamp reflector is assembled to the backlight so as to cover the cold cathode tube. Similar to the direct backlight, the lamp reflector is disposed near the cold cathode tube. At this time, if the surface on which the resin layer of the reflective film (preferably the resin layer containing the ultraviolet absorber and / or the light stabilizer) is formed faces the cold cathode tube side and does not adhere to the stainless plate or the reflecting film, it exits from the cold cathode tube. The white film of a base material may yellow by ultraviolet rays. Therefore, when sticking, it is necessary to distinguish between the surface on which the resin layer is formed and the surface on the opposite side. In the film for surface light source reflecting members of this invention, the surface on which the resin layer was formed and the surface on the opposite side are easy to identify, the work efficiency in an attachment process improves, and productivity also improves.

The reflective film of this invention can be used suitably for the liquid crystal backlight of an inverse prism system. As described above, when assembling the backlight, the case body of the backlight and the reflective film may come into contact and be damaged. In the edge-lit backlight, a cavity is formed in the case body of the backlight for weight reduction, and damage caused to the reflective film is seen through the cavity. As the backlight showing damage is reduced in quality as a finished product, the yield is lowered. When the glossiness of the reflective film is low, the damage generated on the surface becomes inconspicuous. On the other hand, in the reverse prism type liquid crystal backlight, a high glossiness reflective film is required for high brightness. Therefore, by mounting the reflective film of the present invention on the backlight case side with a low glossiness toward the light guide plate side, it is difficult to be noticeable in case of damage required on the backlight case body side, and is required on the light guide plate side. The specular reflection component can make a lot of reflection compatible. That is, the liquid crystal backlight of the anti-prism system using the reflecting film of this invention can improve a yield and can also be made into high brightness, without impairing the quality as a backlit finished product.

(Example)

The measurement method and evaluation method are shown below.

(1) average reflectance

The average reflectance of the surface in which the resin layer of the reflective film was formed is measured by the following procedure. An integrating sphere was attached to a spectrophotometer (U-3310) manufactured by Hitachi High Technologies, and the reflectance when the standard white plate (aluminum oxide) was 100% was measured over 400 to 700 nm. Reflectances are read out at intervals of 5 nm from the obtained chart, and their average values are calculated to be average reflectances. Three samples were measured about each reflective film, and the average value was made into the average reflectance of the reflective film. Moreover, when the resin layer is not formed in the reflective film, the average reflectance of the surface considered as "the surface which formed the resin layer" in the measurement of "(3) glossiness (60 degree)" is measured.

(2) heat shrinkage

(Thermal shrinkage in the length direction)

The sample of 10 mm width (film width direction) x 230 mm length (film longitudinal direction) is cut out from a reflective film. A mark at 200 mm intervals is placed in the longitudinal direction of the sample, and the inter-mark distance is accurately read by a metal letter (L ₀ mm). The sample was left to stand in a hot air oven at 90 ° C. for 30 minutes, and then slowly cooled to room temperature. Next, the inter-mark distance of the sample is read by the above method (L mm). The thermal contraction rate was computed by the following formula from the said mark-to-mark distance, and was represented by%. Three samples were cut out from one reflective film, and the average value of the thermal shrinkage values of each sample was taken as the thermal shrinkage of the reflective film.

Heating shrinkage (%) = (L ₀ -L) / L ₀ × 100

Also, negative values indicate that the film is stretched.

(Thermal shrinkage in the width direction)

The sample of 10 mm width (film longitudinal direction) x 230 mm length (film width direction) was cut out from the reflective film, and it measured like the measuring method of the thermal contraction rate of a longitudinal direction.

(3) Glossiness (60 °)

The glossiness (60 degrees) of both the surface on which the resin layer of the reflective film was formed, and the surface on the opposite side is measured by the following procedures. The glossiness was measured based on JIS K7105 (1981 edition) using the digital variable angle glossmeter (UGV-4D) made by Suga Shikenki. Three samples were measured about each reflective film, and the average value was made into glossiness (60 degree) of a reflective film. In addition, when the resin layer is not formed in the reflective film, the surface of the one with less glossiness (any surface when glossiness is the same on both surfaces) is considered as "the surface which formed the resin layer."

(4) Average reflectance after light resistance test

The reflecting film was put into the ultraviolet-ray deterioration promotion tester eye super UV tester SUV-W131 (made by Iwasaki Denki Co., Ltd.), and the forced ultraviolet irradiation test was done on the following conditions.

"Ultraviolet rays irradiation condition"

Illuminance: 100mW / ㎠, temperature: 60 ° C, relative humidity: 50% RH, irradiation time: 48 hours

The average reflectance was measured according to the method of (1) about the sample after irradiation.

(5) Identification of the surface of the reflective film

Both sides of the reflective film were observed by visual confirmation by ten judges arbitrarily selected. If all 10 people could identify the surface on which the resin layer was formed, and the surface on the opposite side, it determined as (circle), and even if one could not identify, it was x. Each reflecting film was evaluated by one sample.

(6) invisibility of damage

A load of 100 g was applied to the steel wool of # 0000 to the surface on which the resin layer of the reflective film was formed, and reciprocating friction was performed three times at a stroke width of 10 cm and a speed of 30 mm / sec. The surface in which the resin layer was formed by ten arbitrarily selected judges was observed by visual confirmation. If no damage was observed in all 10 people, it was determined as x if damage was seen even in one person. In addition, when the resin layer is not formed in the reflective film, damage is caused to the surface considered as "the surface on which the resin layer was formed" in the measurement of "(3) glossiness (60 °)" Observed. Each reflecting film was evaluated by one sample.

Example 1

First, the master chip which added the chip of polyethylene terephthalate (F20S by Toray Corporation) and the copolymer of polyethyleneglycol, polybutylene terephthalate, and polytetramethylene glycol of molecular weight 4000 at the time of superposition | polymerization of polyethylene terephthalate was 180 degreeC. Vacuum dried at 3 h.

Subsequently, 65 parts by weight of polyethylene terephthalate, 10 parts by weight of 10 mol% of isophthalic acid and 5 mol% of polyethylene glycol copolymerized with polyethylene terephthalate, 5 parts by weight of a copolymer of polybutylene terephthalate and polytetramethylene glycol, poly It mixed so that it might become 20 weight part of methylpentenes. The mixture was fed to extruder B heated to 270-300 ° C. (B layer).

On the other hand, it mixed so that it might become 1 weight part of master chips which contained 97 weight part of chips of polyethylene terephthalate, and 2 weight% of silicon dioxide with a number average particle diameter of 1.5 micrometers. The mixture was vacuum dried at 180 ° C. for 3 hours and then fed to extruder A heated to 280 ° C. (A layer).

These polymers were laminated through a laminating apparatus so as to be A layer / B layer / A layer (thickness ratio A layer: B layer: A layer = 1: 8: 1), and were molded into a sheet form from the T die.

Moreover, this sheet was cooled and solidified by the cooling drum of surface temperature of 25 degreeC, and it was set as the unstretched film. Subsequently, the unstretched film was introduce | transduced into the roll group heated at 85-98 degreeC, it extended | stretched 3.4 times in the film longitudinal direction, and cooled in the roll group of 25 degreeC. Subsequently, both ends of the film longitudinally stretched in the longitudinal direction were introduced into the tenter while being held by the clip, and stretched 3.6 times in the film width direction (direction perpendicular to the film longitudinal direction) in an atmosphere heated at 130 ° C. Then, 230 degreeC heat setting was performed in the tenter, and it cooled slowly evenly, and cooled to room temperature. Finally, it wound up by the winding machine and obtained the white film of 188 micrometers in thickness. The glossiness (60 °) of the obtained white film was 121%.

As a coating liquid for forming a resin layer, Harus Hybrid (registered trademark) UV-G13 {acrylic copolymer, a solution having a concentration of 40%, manufactured by Nippon Shokubai Co., Ltd.}: 41.4 g, death module (registered trademark) N3200 (curing agent) , Concentration 100%, Smica Bayer Urethane Co., Ltd.}: 2.1 g, toluene: 54.5 g, silica powder (Sihorovik (registered trademark 100) manufactured by Fuji-Sirisia Co., Ltd.)}: 1.8 g as inorganic fine particles The coating liquid prepared by adding while preparing was prepared. This coating liquid was applied to one surface of the white film so that the thickness after drying was 3 µm, a resin layer was formed, and dried. Drying of the coating liquid was performed at 130 degreeC for 1 minute. In this way, a reflective film was obtained. The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 25%.

Example 2

A white film was obtained in the same manner as in Example 1 except that the amount of the master chip (2 wt% silicon dioxide content) mixed in the A layer was 2 parts by weight. The glossiness (60 °) of the obtained film was 107%.

A resin layer was formed in the same manner as in Example 1 except that the amount of the silica powder {Saihorobic (registered trademark) 100 manufactured by Fuji-Sirisia Co., Ltd.) was 2.3 g in the coating liquid for forming the resin layer, thereby obtaining a reflective film. . The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 13%.

Example 3

A white film was obtained in the same manner as in Example 1 except that the amount of the master chip (silicon dioxide content 2 wt%) mixed in the A layer was 3.5 parts by weight. The glossiness (60 °) of the obtained film was 95%.

A resin layer was formed in the same manner as in Example 1 except that the amount of the silica powder {Saihorobic (registered trademark) 100 manufactured by Fuji-Sirisia Co., Ltd.)} 2.3 g in the coating liquid for forming the resin layer was formed to obtain a reflective film. . The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 12%.

Example 4

The polymer composition of the A layer and the B layer, and the temperatures of the extruder A and the extruder B were the same as in Example 1.

97 parts by weight of chips of polyethylene terephthalate and 3.5 parts by weight of a master chip containing 2% by weight of silicon dioxide having a number average particle diameter of 1.5 µm were mixed. The mixture was vacuum dried at 180 ° C. for 3 hours and then fed to extruder C heated to 280 ° C. (C layer).

These polymers were laminated through a laminating apparatus so as to be A layer / B layer / C layer (thickness ratio A layer: B layer: C layer = 1: 8: 1), and were molded into a sheet form from the T die.

In addition, this sheet was stretched under the same conditions as in Example 1 to obtain a white film. The glossiness (60 degrees) of the obtained white film was A layer side: 121%, C layer side: 95%.

A resin layer was formed on the surface of the layer A in the same manner as in Example 1, except that the amount of the silica powder {Saihorobi (registered trademark) 100 manufactured by Fuji-Sirisia Co., Ltd.) was 2.3 g in the coating liquid for forming the resin layer. A film was obtained. The glossiness (60 °) of the surface on which the resin layer of the reflective film was formed was 14%.

(Comparative Example 1)

A reflective film was obtained in the same manner as in Example 1 except that the resin layer was not formed.

(Comparative Example 2)

A resin layer was formed in the same manner as in Example 1 except that the amount of the silica powder {Saihorobi (registered trademark) 100 manufactured by Fuji-Sirisia Co., Ltd.) in the coating liquid for forming the resin layer was 0.3 g, to obtain a reflective film. . The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 70%.

(Comparative Example 3)

A resin layer was formed in the same manner as in Example 1 except that the amount of the silica powder {Saihorobic (registered trademark) 100 manufactured by Fuji-Sirisia Co., Ltd.) in the coating liquid for forming the resin layer was 0.9 g, to thereby obtain a reflective film. . The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 50%.

(Comparative Example 4)

The resin layer described in Example 1 was disposed on one side of a white film made of 188 μm porous biaxially stretched polyethylene terephthalate (Lumira (registered trademark) E60L manufactured by Toray Corporation, Glossiness (60 °): 30%). It formed and the reflective film was obtained. The glossiness (60 degrees) of the surface in which the resin layer of the reflective film was formed was 25%.

In Examples 1 to 4, the difference in glossiness was greater than 80%, and it was easy to identify the surface on which the resin layer was formed and the surface on the opposite side. Moreover, in Examples 1-4, the glossiness of the surface with a small glossiness (surface in which the resin layer was formed) was 25% or less, and the damage of the surface was also hard to be seen.

On the other hand, in Comparative Examples 1-4, the glossiness difference was 80% or less, and it was difficult to distinguish the surface in which the resin layer was formed, and the surface on the opposite side. In Comparative Examples 1 and 2, the glossiness of the surface having a low glossiness (the surface on which the resin layer was formed) was greater than 50%, and damage to the surface was also confirmed.

The film for surface light source reflecting members of this invention can be used suitably for a liquid crystal backlight. In particular, it can use suitably for the direct type | mold liquid crystal backlight, the liquid crystal backlight of an inverted prism system, and the lamp reflector for liquid crystal backlights.

Claims (9)

It consists of a white film, and the difference (DELTA) G of the glossiness (60 degree) of one surface and the other surface is (DELTA) G> 80%, The film for surface light source reflection members characterized by the above-mentioned. The film for surface light source reflection members according to claim 1, wherein the surface of the white film has a resin layer, and the glossiness (60 °) of the other surface of the white film is 90% or more. 3. The film for a surface light source reflection member according to claim 2, wherein the resin layer is a resin layer containing an ultraviolet absorber and / or a light stabilizer. The film for surface light source reflection member according to claim 1, wherein the heat shrinkage in the film length direction and the film width direction after heat treatment at 90 ° C. for 30 minutes is -0.1% or more and 0.2% or less. The method of claim 1, wherein the white film is composed of a three-layer structure of A layer / B layer / A layer, B layer is a layer containing fine bubbles, A layer is inorganic particles and / or organic particles in polyester And the particle content is 0.5 weight% or less with respect to the total weight of each A layer, The film for surface light source reflection members characterized by the above-mentioned. The method of claim 1, wherein the white film is composed of a three-layer structure of A layer / B layer / C layer, B layer is a layer containing fine bubbles, A layer and / or C layer is inorganic particles in polyester And / or a layer containing organic particles, the particle content of which is 0.5% by weight or less with respect to the total weight of the respective layers containing particles. The film for surface light source reflecting members of any one of Claims 1-6 was used, The liquid crystal backlight of the direct type | mold system. The film reflector as described in any one of Claims 1-6 was used, The lamp reflector for liquid crystal backlights characterized by the above-mentioned. The film for surface light source reflection members of any one of Claims 1-6 was used, The liquid crystal backlight of the inverse prism system characterized by the above-mentioned.

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