JP2003048291A - Transflective reflective laminated polyester film and manufacturing method - Google Patents

Abstract

(57) [Summary] (Modified) [PROBLEMS] To provide excellent visibility of a liquid crystal display in both transmitted light and reflected light, and to provide a temporal adhesion between a liquid crystal display member and a transflective laminated polyester film. Provide a high transflective laminated polyester film for liquid crystal display. SOLUTION: The polyester layer (A) is (a) a plate-like filler having an average major axis of 0.5 to 200 μm, which is oriented at an orientation angle of 30 ° or less in a plane direction of the film, and (b) a shape factor is 2 or more. The polyester layer (B) contains 0.1 to 30% by weight of either a dispersed phase of a thermoplastic resin other than polyester or (c) spherical particles having an average particle size of 0.5 to 200 μm, and the polyester layer (B) has an average particle size of 0. Characterized in that it contains 0.01 to 5% by weight of inert particles having a wavelength of 550 n, which is stretched in at least one axial direction and is at least two layers.
The transflective laminated polyester film having a total light reflectance of 40% or more at m, a total light transmittance of 20% or more, and a sum of the total light reflectance and the total light transmittance of 80% or more.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transflective laminated polyester film and a method for producing the same. More specifically, a semitransparent reflective laminated polyester film having a semitransparent reflective performance of a polyester film base material itself, which is used for a light source part of a liquid crystal display device having excellent visibility when using reflected light and transmitted light, and its production. It is about the method.

[0002]

2. Description of the Related Art In recent years, liquid crystal displays are easier to make lighter, thinner and smaller than CRT displays, and consume less power. Therefore, they are rapidly becoming display devices for personal computers, car navigation systems, PDAs, mobile phones, etc. Is becoming popular. However, since the liquid crystal display body needs transmitted light from the opposite side of the liquid crystal cell to see the display, a light source for display recognition is necessary, and the liquid crystal display body is power saving. However, in the display of mobile electronic devices such as mobile phones and PDAs, the power consumption thereof is large, which is a factor limiting the usage time of these devices.

In order to solve this problem, a transflective liquid crystal display device is used. The transflective liquid crystal display device uses external light, and when the ambient environment is bright, the display can be recognized by the reflected light, and when the ambient environment is dark, the semitransparent property is used to turn on the built-in light source. The display is recognizable.

However, even in the transflective liquid crystal display device, it is very difficult to secure sufficient visibility in both display by reflected light and display by transmitted light. This is because if it is attempted to obtain sufficient visibility by reflected light, the visibility due to transmitted light is extremely reduced, and conversely, if it is attempted to obtain sufficient visibility due to transmitted light, the visibility due to reflected light is extremely reduced. .

As a method for obtaining good visibility in both transmitted light and reflected light, Japanese Patent Laid-Open Nos. 8-179125, 11-231114, and 11-2 are available.
In Japanese Patent No. 71512, there is proposed a method in which a semi-transmissive reflective layer containing a pearl pigment (hereinafter referred to as tabular mica particles coated with titanium dioxide, iron oxide or the like) is applied on a film substrate. However, there is a problem that it is difficult to obtain good reflection characteristics when the pearl pigment is not oriented in the plane direction of the film substrate. Therefore, as a method of orienting the pearl pigment in the semi-transmissive reflective layer, for example, a method of applying shear stress to the coating liquid layer forming the semi-transmissive reflective layer has been proposed. It is necessary to adjust the shear rate of the liquid layer or the shear rate of the coating liquid supply member and the coated sheet, and it is not easy to adjust the coating speed and the appearance that varies depending on the shear rate.

Further, if the adhesiveness at the interface between the film substrate and the semi-transmissive reflective layer is insufficient, peeling may occur over time. Further, the semi-transmissive reflective layer obtained by coating is easily attacked by an organic solvent and the like, which may cause trouble during the processing step. Further, when the concentration of the pearl pigment in the coating liquid is increased for the purpose of improving the reflectance, the strength of the semi-transmissive reflective layer obtained is lowered and the cohesive failure is likely to occur.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel transflective laminated polyester film suitable for liquid crystal display and a method for producing them, which does not have the problems and drawbacks described above. It is in. For more details,
A state in which good visibility is obtained in transmitted light using the backlight of the liquid crystal display unit as a light source, and at the same time, an additive that reflects and diffuses visible light is placed in the film substrate so that its characteristics can be exhibited. By using the method of containing in, excellent visibility of the liquid crystal display in both transmitted light and reflected light, further enhance the adhesiveness with time of the liquid crystal display member and the semi-transmissive reflective laminated polyester film, by a laminated structure An object of the present invention is to provide a transflective laminated polyester film suitable for liquid crystal display, which has high film forming stability.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has at least uniaxially stretched film composed of a polyester layer (A) and a polyester layer (B). A laminated polyester film having two or more layers, wherein the total light reflectance at a wavelength of 550 nm is at least 40% or more, the total light transmittance at the wavelength is at least 20% or more, and the above-mentioned total light reflectance and total light transmittance. Of 80% or more, and the polyester layer (A) is oriented in the plane direction of the polyester film in the layers (a) and (A) at an orientation angle of 30 ° or less and an average major axis of 0.5 to 200 μm. Filler,
Either (b) a dispersed phase of a thermoplastic resin other than polyester having a shape factor of 2 or more in the (A) layer, or (c) spherical particles having an average particle size of 0.5 to 200 μm in the (A) layer. On the other hand, the polyester layer (B) contains 0.1 to 30% by weight in total, and the polyester layer (B) contains 0.01 to 5% by weight of inert particles having an average particle diameter of 0.01 to 5 μm with respect to the layer (B). Therefore, a semi-transmissive reflective laminated polyester film having excellent visibility of liquid crystal display in both transmitted light and reflected light, and further, high adhesion over time between the liquid crystal display member and the semi-transmissive reflective polyester film, and having a laminated constitution It was found that a semi-transmissive reflective laminated polyester film having high film-forming stability can be obtained in the above, and thus completed the present invention.

That is, the transflective laminated polyester film suitable for liquid crystal display according to the present invention comprises at least two uniaxially stretched layers comprising a polyester layer (A) and a polyester layer (B). A laminated polyester film having a total light reflectance of at least 40% at a wavelength of 550 nm, a total light transmittance of at least 20% at the above wavelength, and a sum of the total light reflectance and the total light transmittance of 80. % Or more, and the polyester layer (A) is oriented at an orientation angle of 30 ° or less in the plane direction of the polyester film in the (a) and (A) layers, a plate-like filler having an average major axis of 0.5 to 200 μm, ( b) A dispersed phase of a thermoplastic resin other than polyester having a shape factor of 2 or more in the layer (A), or (c) an average particle size of 0.5 to 200 μm. One of the spherical particles (A)
The polyester layer (B) contains a total of 0.1 to 30% by weight, and the polyester layer (B) contains 0.01 to 5% by weight of inert particles having an average particle diameter of 0.01 to 5 μm with respect to the layer (B). It is a transflective laminated polyester film containing.

In a preferred embodiment of the present invention, the plate-like filler is a pearl pigment, the thermoplastic resin is a polyolefin resin, and the polyolefin resin is a poly-4-methyl-1-pentene resin. , The spherical particles are titanium oxide and / or calcium carbonate.

Further, a semi-transmissive reflective laminated polyester film having an adhesive layer on at least one side of the polyester film and a semi-transmissive reflective laminated polyester film having a hard coat layer on at least one side of the polyester film are also included as a preferred embodiment of the present invention. To be done.

The present invention also provides (a) an average major axis of 0.5 to
200 μm and 3 in the plane direction of the film by stretching
A plate-like filler which is oriented at an orientation angle of 0 ° or less,
(B) a thermoplastic resin other than polyester, which has a shape factor of 2 or more in the polyester layer (A) by stretching,
Alternatively, (c) a total of 0.1 to 30% by weight of spherical particles having an average particle size of 0.5 to 200 μm with respect to the layer (A).
Polyester layer (A) contained, and average particle size 0.0
Inert particles of 1 to 5 μm are added to the layer (B) in an amount of 0.01 to
A laminated unstretched polyester film composed of the polyester layer (B) contained in an amount of 5% by weight was stretched at a draw ratio of 2.0 to 4.
By stretching at least uniaxially by 0 times,
A transflective laminated polyester film can be produced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The constitution of the present invention will be described in more detail below. <Polyester film> The polyester constituting the polyester layer (A) and the polyester layer (B) in the present invention is preferably a crystalline linear saturated polyester composed of an aromatic dicarboxylic acid component and a diol component, for example polyethylene. Examples thereof include terephthalate, polyethylene isophthalate, polybutylene terephthalate and polyethylene-2,6-naphthalate. Further, these polyesters may be homopolymers and copolymers in which copolymer components other than the main constituent components are appropriately copolymerized within a range not impairing the heat distortion resistance of the film. Among these, a polyethylene terephthalate copolymer is particularly preferable from the viewpoint of film forming property and transparency. Here, the "main constituent" means that at least 75 mol% or more, preferably at least 85 mol% or more of all repeating units of the polyester are ethylene terephthalate units, ethylene isophthalate units, tetramethylene terephthalate units, or ethylene-2,6. -Means naphthalene dicarboxylate units.

Examples of the above-mentioned copolymerization component include, as dicarboxylic acid components, aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid. Acids, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and examples of the diol component include aliphatic diols such as tetramethylene glycol and hexamethylene glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. These copolymerization components may be used alone or in combination of two or more. Among these, isophthalic acid is mentioned as a particularly preferable copolymerization component from the viewpoint of stretchability during film formation. These copolymerization components are used in the range of less than 25 mol%, more preferably less than 15 mol% of all repeating units of the polyester.

The polyester is glycerin,
Even if it is a copolymer of a component having three or more ester-forming functional groups such as pentaerythritol, trimellitic acid, pyromellitic acid, etc. in an extremely small amount (a range in which a substantially linear polymer can be obtained) Good. Alternatively, a part or all of the terminal hydroxyl group and / or carboxyl group is blocked with a compound having one ester-forming functional group such as benzoic acid or methoxypolyalkylene glycol in order to improve hydrolysis resistance. May be

The intrinsic viscosity of polyester (orthochlorophenol, 35 ° C.) is 0.40 dl / g to 1.50 dl.
/ G is preferable, more preferably 0.45d
1 / g to 1.20 dl / g. Intrinsic viscosity 0.40
When it is less than dl / g, the mechanical properties required for the polyester film as a semi-transmissive reflective laminated film substrate, such as tear strength, may be insufficient. On the other hand, when the intrinsic viscosity exceeds 1.50 dl / g, the productivity in the raw material manufacturing process and the film forming process is impaired.

The polyester constituting the film of the present invention is not limited by its production method. For example,
As a method for producing a homopolymer of polyethylene terephthalate or a copolymer thereof, an esterification reaction of terephthalic acid, ethylene glycol and a copolymerization component added as necessary, and the resulting reaction product is further polycondensed to produce a polyester. Is preferably used.

Additives such as a fluorescent brightening agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a flame retardant and an antistatic agent can be added to the polyester film, if necessary.

<Plate Filler> The semitransparent reflective laminated polyester film of the present invention contains a plate filler in the polyester layer (A) in order to impart visibility of liquid crystal display in both transmitted light and reflected light. It is preferable.
As the plate-like filler, the type is particularly limited as long as it is an inorganic compound having a plate-like shape, the ratio of the average major axis consisting of the major axis of the flat plate-shaped surface and the thickness of the plate-like filler is 1.1 or more. However, examples thereof include pearl pigment, barium sulfate, plate boehmite, and kaolin. These plate-like fillers may be used alone or in combination of two or more. Here, the “average major axis” is the maximum diameter of the flat plate-like surfaces of a certain number of plate-like fillers, that is, the average value of the major axis.

The pearl pigment in the present invention is a tabular mica particle coated with titanium dioxide, iron oxide or the like, which is commercially available as a pearl pigment. The coverage of the surface of the tabular mica particles with titanium dioxide is in the range of 10% to 50%. Examples of such pearl pigments include “Iriodin” (manufactured by Merck Japan) and “Mearlin” (manufactured by Marl).

The average major axis of the plate-like filler in the present invention must be 0.5 to 200 μm. The average major axis of the plate-like filler of the present invention is preferably 0.8 to
180 μm, more preferably 1-125 μm.
When the average major axis of the plate-like filler is less than 0.5 μm, sufficient reflection characteristics cannot be obtained. Further, when the average major axis of the plate-like filler exceeds 200 μm, the smoothness of the polyester film is lost and the visibility is also reduced.

The thickness of the plate-like filler is 0.01 to
It is preferably 10 μm. When it is less than 0.01 μm, it is difficult to obtain sufficient reflection characteristics, and the plate-like filler is easily broken in the film forming process. Also 10μ
When it exceeds m, the plate-like characteristics are likely to be lost, the orientation of the plate-like filler is lowered by stretching, and it becomes difficult to obtain visibility in reflected light and transmitted light.

It is necessary that the plate-like filler is oriented in the plane direction of the film in the transflective laminated polyester film at an orientation angle of 30 ° or less. The orientation angle of the plate-like filler is more preferably 15% or less. Here, the "orientation angle" refers to the average value of the angles formed by the flat surface of a certain number of plate fillers and the flat surface of the polyester film. Specifically, an arbitrary cross section of the obtained transflective laminated polyester film was photographed with a scanning electron microscope (JSM-5200, manufactured by JEOL Ltd.) to obtain 100 plate-like fillers. The orientation angle of the flat surface of the filler with respect to the polyester film surface is measured and an average value is calculated, and the value is defined as the "orientation angle". When the orientation angle of the plate-like filler contained in the polyester layer (A) is larger than 30 °, high visibility in reflected light cannot be obtained.

The plate-like filler in the present invention may be added before the end of the transesterification reaction during the polyester synthesis or before the start of the polycondensation reaction, or during the polyester film formation. . Further, by preliminarily producing master pellets to which a large amount of plate-like fillers have been added, during polyester synthesis, or during polyester film formation, kneading with polyester not containing plate-like fillers and adjusting the concentration to a predetermined amount. It may be. In addition, when adding a plate-like filler at the time of polyester synthesis, it is preferable to disperse these in a diol component and then add it as a slurry to the reaction system.

<Thermoplastic Resin Other Than Polyester> The transflective laminated polyester film of the present invention includes
The polyester layer (A) preferably contains a thermoplastic resin other than polyester in order to provide visibility of the liquid crystal display with both transmitted light and reflected light. The thermoplastic resin is preferably a resin that can be deformed so as to be stretched in the stretching direction by stretching the polyester film, and specific examples thereof include the following. Examples of the polyolefin resin include polyethylene, polypropylene, poly-3-methyl-1-butene, poly-4-methyl-1-pentene, and examples of the polystyrene resin include polystyrene, polymethylstyrene, polydimethylstyrene, polyfluorostyrene, poly-2. -Methyl-4-fluorostyrene, other, polybutadiene, polyvinyl-t-butyl ether, cellulose triacetate, cellulose tripropionate, polyvinyl fluoride, polychlorotrifluoroethylene, methacrylic resin, polyamide resin and the like. Above all,
From the viewpoint of visibility of transmitted light and reflected light, a polyolefin resin, particularly poly-4-methyl-1-pentene is preferable. These thermoplastic resins may be used alone or in combination of two or more.

The thermoplastic resin other than polyester in the present invention must have a shape factor of 2 or more in the transflective laminated polyester film. Further, the thermoplastic resin preferably has a shape factor of 3 or more. If the shape factor of the thermoplastic resin other than polyester is less than 2, the reflection characteristics are deteriorated and the visibility in reflected light becomes insufficient.

Here, the "shape factor" is a numerical expression of the shape of the thermoplastic resin other than polyester dispersed in the semi-transmissive reflective laminated polyester film, and has a structure close to a spherical shape due to stretching during film formation. It is defined as the major axis / minor axis in the stretched shape. Specifically, an arbitrary cross section of the obtained semi-transmissive reflective laminated polyester film is scanned with a scanning electron microscope (JSM-52, manufactured by JEOL Ltd.).
At 00), a photograph is taken, and the major axis / minor axis of any 100 cross sections of the thermoplastic resin is measured with an image analyzer, and the average value is defined as the "shape factor".

In addition, in order for the thermoplastic resin other than the polyester in the present invention to be stretched into a flat plate shape in the stretching step during film formation and the shape factor to be 2 or more, the polyester and the thermoplastic resin other than polyester may be used. It is preferable that the plastic resin and the plastic resin are incompatible with each other. Where "incompatible"
Means that the difference in solubility parameter δ (SP value) is 1 [ca
1 / cm ³ ] ^1/2 or more. When the difference in SP value is 1 [cal / cm ³ ] ^1/2 or more, the polyester and the thermoplastic resin other than polyester have no affinity with each other, so that a sea-island structure is likely to be formed, and the stress in the stretching process may cause , The thermoplastic resin other than polyester forming the island phase is easily stretched out in a flat plate shape. On the other hand, S
When the difference in P value is less than 1 [cal / cm ³ ] ^1/2 , the resins are easily compatible with each other, and even if a sea-island structure is formed,
Since the thermoplastic resin other than polyester is a minute island phase of less than 1 μm, it tends to be difficult to be deformed by stress during stretching.

The thermoplastic resin other than polyester in the present invention is preferably added at the time of forming a polyester film.

<Spherical Particles> The semitransparent reflective laminated polyester film of the present invention may contain spherical particles in the polyester layer (A) in order to provide visibility of liquid crystal display in both transmitted light and reflected light. preferable. The spherical particles preferably have a spherical shape,
Examples of the inorganic spherical particles include titanium oxide and calcium carbonate, and examples of the organic spherical particles include crosslinked polystyrene resin and crosslinked silicone resin. Among these, titanium oxide and calcium carbonate are particularly preferable. These spherical particles may be used alone or in combination of two or more.

The average particle size of the spherical particles in the present invention is
It is preferably 0.5 to 200 μm. The average particle size of the spherical particles is preferably 0.8 to 180 μm.
m, and more preferably 1-125 μm. If the average particle diameter of the spherical particles is less than 0.5 μm, sufficient reflection characteristics cannot be obtained. The average particle size of the spherical particles is 200 μm.
If it exceeds, the smoothness of the polyester film is lost and the visibility is also reduced.

In the present invention, there are a number of factors for the effect of the spherical particles to improve the visibility in reflected light. In the case of spherical particles having a low hardness, the particles are crushed during the kneading and stretching steps and have a shape close to a plate. It is conceivable that In the case of spherical particles having a strong cohesive force, it is considered that when they are subjected to stress in the stretching step, they are oriented into a plate-like shape in the state of aggregated particles. The generation of fine voids at the interface with and is also considered as one factor.

The spherical particles in the present invention may be added before the completion of the transesterification reaction or the start of the polycondensation reaction during the polyester synthesis, or may be added during the polyester film formation. Further, it is a method of preparing master pellets to which a large amount of spherical particles have been added in advance, kneading with polyester not containing spherical particles at the time of polyester synthesis or polyester film formation, and adjusting the concentration to a predetermined amount. Good. When spherical particles are added at the time of polyester synthesis, it is preferable to disperse these in a diol component and then add them as a slurry to the reaction system.

These plate-like filler, thermoplastic resin other than polyester, and spherical particles may be used alone or in combination. Among these, as a preferred embodiment, plate-like filler alone, thermoplastic resin other than polyester alone, spherical particles alone, combination of plate-like filler and thermoplastic resin other than polyester, combination of plate-like filler and spherical particles, A combination of a thermoplastic resin other than polyester and spherical particles can be used.

The addition amount of any one of the plate-like filler, the thermoplastic resin other than polyester, or the spherical particles in the present invention is 0.1 to 30% by weight in total based on the weight of the polyester layer (A). It is preferable. Also,
The plate-shaped filler, a thermoplastic resin other than polyester,
Alternatively, the total addition amount of either spherical particles is 0.3 to
It is more preferably 28% by weight, and further 0.5 to
It is preferably 25% by weight. If the addition amount of any one of the plate-like filler, the thermoplastic resin other than polyester, or the spherical particles is less than 0.1% by weight, sufficient visibility in reflected light cannot be obtained, while if it exceeds 30% by weight, The stretchability of the polyester film is deteriorated, and the productivity including the film-forming stability is reduced even with a laminated structure.

<Other Additives> In the semi-transmissive reflective laminated polyester film of the present invention, if necessary, the cleavage resistance of the polyester film may be improved and the stretchability of the polyester film may be significantly improved. The polyester layer (A) may contain a low specific gravity agent. Examples of the specific gravity reducing agent include polyethylene glycol, methoxy polyethylene glycol, polypropylene glycol, polyalkylene glycols such as polytetramethylene glycol, copolymers of ethylene oxide and propylene oxide, sodium dodecylbenzenesulfonate, sodium alkylsulfonate, Examples thereof include glycerin monostearate and tetrabutylphosphonium paraaminobenzene sulfonate. Among them, polyethylene glycol is preferable. The addition amount of these specific gravity reducing agents is not particularly limited as long as it does not impair the object of the present invention, but is preferably the polyester layer (A).
Is 10% by weight or less, and more preferably 8% by weight or less. Addition amount of low specific gravity agent is 10% by weight
If it exceeds, the low-density material may have a bad influence such as precipitation on the surface of the polyester film or bleeding out.

The semitransparent reflective laminated polyester film of the present invention may further contain a thermoplastic polyester elastomer in the polyester layer (A) for the purpose of improving the stretchability of the polyester film, if necessary. . Examples of such thermoplastic polyester elastomers include polyether ester block copolymers in which the hard segment is mainly made of thermoplastic aromatic polyester and the soft segment is mainly polyalkylene oxide.

The thermoplastic aromatic polyester constituting the hard segment is a polyester formed from an aromatic dicarboxylic acid or its ester-forming derivative and an aliphatic diol, preferably terephthalic acid and / or dimethyl terephthalate and 1 , 4-butanediol is a polybutylene terephthalate which is used as a main constituent component of at least 60 mol% or more, more preferably 70 mol% or more of all repeating units of the hard segment. Further, these thermoplastic aromatic polyesters may be a copolymer obtained by appropriately copolymerizing a copolymerization component other than the main constituent components such as a homopolymer made of polybutylene terephthalate.

Examples of the above-mentioned copolymerization component include isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-
Dicarboxylic acid components such as 4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sulfoisophthalic acid, or their ester-forming derivatives, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl Examples thereof include aliphatic diols such as glycol and decamethylene glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol and tricyclodecanedimethylol. These copolymerization components may be used alone or in combination of two or more. Such a copolymerization component is used in the range of less than 40 mol% and more preferably less than 30 mol% of all repeating units of the hard segment. Examples of the polyalkylene oxide constituting the soft segment include polyethylene oxide having an average molecular weight of about 400 to 5000, polypropylene oxide, polytetramethylene oxide, a copolymer of ethylene oxide and propylene oxide, and a copolymer of ethylene oxide and tetrahydrofuran. Preferred examples thereof include polytetramethylene oxide and copolymers of ethylene oxide and propylene oxide. In addition, you may use together the polyalkylene oxide which comprises these soft segments by 1 type (s) or 2 or more types.

In these thermoplastic polyester elastomers, the weight ratio of the hard segment to the soft segment is 90/10 to 20/80, preferably 85.
/ 15 to 25/75. If there are more hard segments than this, flexibility may be insufficient, and if there are more soft segments than this, the crystallinity may be lowered and the film processability may be impaired.

The addition amount of these thermoplastic polyester elastomers is not particularly limited as long as the object of the present invention is not impaired, but is preferably 10% by weight or less, more preferably 8% by weight based on the weight of the polyester layer (A).
It is less than or equal to weight%. If the addition amount of the thermoplastic polyester elastomer exceeds 10% by weight, the heat resistance and mechanical properties of the polyester film may be impaired.

The low specific gravity agent and the thermoplastic elastomer may be used alone or in combination.

<Inert Particles> The semitransparent reflective laminated polyester film of the present invention includes a polyester layer (B).
It is preferable to contain inert particles. Examples of such inert particles include inorganic fine particles containing elements of IIA, IIB, IVA, and IVB of the periodic table (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, barium sulfate, etc.), Examples thereof include organic fine particles made of a polymer having high heat resistance such as crosslinked silicone resin, crosslinked polystyrene, and crosslinked acrylic resin, and they may be used alone or in combination of two or more kinds. The average particle size of these inert particles is 0.01 to 5 μm, more preferably 0.0 to 5 μm.
The thickness is preferably 5 to 3 μm, more preferably 0.1 to 2 μm. When the average particle diameter of the inert particles is less than 0.01 μm, the dispersion in the polyester layer (B) tends to be poor, while when it exceeds 5 μm, the transmittance may be decreased or the film-forming stability may be deteriorated. It is not preferable because Also,
The preferable amount of the inert particles added is 0.01 to 5% by weight based on the weight of the polyester layer (B). When the amount of the inert particles added is less than 0.01% by weight, the slipperiness of the polyester film during winding and the handling property during surface processing are likely to deteriorate, while 5
If it exceeds 5% by weight, the transmittance is lowered and the film-forming stability is lowered, which is not preferable. The inert particles may be added either at the polymerization stage of the polyester or at the time of film formation.

<Fluorescent Whitening Agent> The semitransparent reflective laminated polyester film of the present invention has a polyester layer (A) and / or a polyester layer (B) for the purpose of improving the reflectance in the wavelength region of 330 to 380 nm. Further, a fluorescent whitening agent may be used.

Examples of such fluorescent whitening agents include OB-1 (manufactured by Eastman) and Uvitex-OB.
(Manufactured by Ciba Geigy), Uvitex-MD (manufactured by Ciba Geigy), JP-Conc (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and the like. The amount of the fluorescent whitening agent added is 0.001 to 0.
It is 1% by weight, preferably 0.005 to 0.05% by weight, and more preferably 0.01 to 0.05% by weight. 0.
When it is less than 001% by weight, the reflectance in the wavelength region of 330 to 380 nm is not improved, while when it exceeds 0.1% by weight, the characteristic color of the fluorescent whitening agent is colored, which is not preferable. It is particularly preferable that the fluorescent whitening agent is contained in at least the outermost layer of the transflective laminated polyester film of the present invention.

The addition of these inert particles and optical brightener is
It may be added at the polymerization stage of polyester, or may be added at the time of forming a polyester film.

<Adhesive Layer> The semi-transmissive reflective laminated polyester film used in the present invention has an adhesive layer on at least one side of the polyester film, so that it can be bonded to a liquid crystal display part composed of a polarizing film or a backlight. it can. The pressure-sensitive adhesive used is not particularly limited, but acrylic-based, rubber-based, and urethane-based pressure-sensitive adhesives are preferably used.

The thickness of the adhesive layer is preferably 0.5 to 60 μm. If the thickness of the adhesive layer is less than 0.5 μm, sufficient adhesiveness cannot be obtained, and if it exceeds 60 μm, it is difficult to extrude or wind the adhesive from the end face, and the handling property in the manufacturing process of the film deteriorates. Moreover, the thickness of the adhesive layer is more preferably 2 to 40 μm.

<Hard Coat Layer> The semi-transmissive reflective laminated polyester film used in the present invention has a hard coat layer on at least one side of the polyester film, so that the semi-transmissive reflective laminated polyester film and the liquid crystal display part or the backlight part can be formed. It is possible to prevent the semi-transmissive reflective laminated polyester film from being scratched in the process of stacking, storing and transporting the intermediate parts to which the and are attached, and to prevent the yield of the final product.

Examples of the material used for the hard coat layer include silane-based and radiation-curable materials that are commonly used. Particularly, radiation-curable hard coat materials are preferable, and ultraviolet (UV) curing is particularly preferable. A hard coat material of the type is preferably used.

Examples of the UV curable material used for forming the hard coat layer include urethane-acrylate type, epoxy-acrylate type and polyester-acrylate type. In order to laminate a hard coat layer on a transflective laminated polyester film, a material for forming the hard coat layer is applied on at least one side of the polyester film, and the material is cured by heating, irradiation with radiation (for example, ultraviolet rays) or the like. Let

The hard coat layer has a thickness of 0.5 to 10 μm.
Is preferred. If the thickness of the hard coat layer is less than 0.5 μm, the intermediate component cannot be sufficiently protected, and if it exceeds 10 μm, curing due to heating or radiation cannot be sufficiently obtained, and blocking easily occurs. The thickness of the hard coat layer is more preferably 1 to 5 μm.

<Total Light Transmittance and Total Light Reflectance> In order to obtain sufficient visibility in transmitted light and reflected light which is the object of the present invention, the total light transmittance and total light of the semi-transmissive reflective laminated polyester film are It is necessary that the reflectance satisfies the following numerical conditions. Where "total light transmittance"
Is the percentage of the amount of light transmitted through the polyester film when the semitransparent-reflection laminated polyester film is irradiated with light having a wavelength of 550 nm measured by an ultraviolet / visible spectrophotometer. The "total light reflectance" refers to the value of the amount of light reflected by the polyester film, which is measured according to the same measurement method.

In the present invention, the total light transmittance at 550 nm of the transflective laminated polyester film is at least 20% or more, and more preferably 25% or more. If the total light transmittance of the semi-transmissive reflective polyester film is less than 20%, sufficient visibility in transmitted light cannot be obtained.

Similarly, in order to obtain sufficient visibility in reflected light, a transflective laminated polyester film of 550 is used.
The total light reflectance in nm is at least 40% or more, and more preferably 50% or more. When the total light reflectance of the semi-transmissive reflective laminated film is less than 40%, sufficient visibility in reflected light cannot be obtained.

Further, in order to obtain a display which is sufficiently bright in both transmitted light and reflected light and has excellent visibility, the sum of the total light transmittance and the total light reflectance at 550 nm of the semi-transmissive reflective laminated polyester film is 80. % Or more, and more preferably 90% or more. When the sum of the total light transmittance and the total light reflectance is less than the above numerical value, the other one is inferior even if either the transmission visibility or the reflection visibility is excellent, and as a semi-transmissive reflective laminated polyester film. It cannot satisfy sufficient performance.

<Layer Structure of Laminated Film> The layer structure of the transflective laminated polyester film in the present invention comprises a polyester layer (A) containing a plate-like filler, a thermoplastic resin other than polyester, or spherical particles. It is composed of a polyester layer (B) containing inert particles, and the number of layers is not particularly limited. The layer structure in the present invention includes, for example, an A / B (where / indicates a layer structure) type two-layer structure, a B / A / B type three-layer structure, and a B / A.
/ B / A / B type five-layer structure, or a multi-layer structure such as seven layers, nine layers, and (n + 1) layers (where n represents an even integer) in the state where the A layer and the B layer are alternately present. Among them, 2 layers, 3 layers and 5 layers are preferable, and 2 layers are particularly preferable. Here, when used as a product, the outermost layer forming the side to be used is preferably composed of a polyester layer (B) containing inert particles. Since the polyester layer (B) containing the inert particles is present in the outermost layer, a plate-like filler, a thermoplastic resin other than polyester,
Or a polyester layer (A) containing either spherical particles
The deterioration of the film-forming property of the film due to the additive, which is a problem with the single-layer film, is likely to be improved.

When each of the polyester layer (A) and the polyester layer (B) is composed of two or more layers, either one of the A layer and the B layer or both layers is composed of two or more compositions. It may be a thing. For example, layer B is 2
B1 when composed of two types of compositions (B1, B2)
/ A / B2 type 3-layer structure, B1 / A / B2 / A / B
An example is one type of five-layer structure.

In the transflective laminated polyester film of the present invention, the ratio (an / bn) of the total layer thickness (an) of the A layer and the total layer thickness (bn) of the B layer is:
It is preferably 0.01 to 5. The layer thickness ratio is such that the layer structure is A1 (thickness: a1) / B1 (thickness: b
1) / A2 (thickness: a2)
It is represented by (a1 + a2) / (b1). If the layer thickness ratio is less than 0.01, it becomes difficult to control the layer thickness and it is difficult to obtain stable quality. On the other hand, the layer thickness ratio is 5
If it exceeds, the discharge balance of each polyester layer is too different, and stable film formation becomes difficult. The layer thickness ratio is 0.
It is more preferably 03 to 3, and particularly preferably 0.05 to 1.

The total thickness of the transflective laminated polyester film is not particularly limited, but is 3 to 250 μm.
m, and more preferably 5 to 75 μm. When the thickness of the transflective laminated polyester film is less than 3 μm, the visibility in reflected light is insufficient. Further, if the thickness of the transflective laminated polyester film is less than 3 μm, even if the amount of the plate-like particles added is increased to a sufficient level for reflected light, a slight difference in coating thickness is likely to appear as streaks. On the other hand, when the thickness of the transflective laminated polyester film exceeds 250 μm, the rigidity of the film becomes strong and the handling property deteriorates, resulting in a decrease in productivity. When the thickness of the transflective laminated polyester film is more than 250 μm, the loss of the transmitted light passing through the polyester film is increased and the visibility is lowered.

The thickness of each of the polyester layer (A) and the polyester layer (B) is 0.01 to 1 μm.
It is preferably m.

<Production Method> The transflective laminated polyester film of the present invention is formed into a biaxially stretched film by a known method such as a sequential biaxial stretching method, a simultaneous biaxial stretching method or an inflation method. . Moreover, a simultaneous multilayer extrusion method is mentioned as a lamination method. Specific example 2
The case of a layer film (B / A) will be described below as an example.

Here, a plate-like filler having an average major axis of 0.5 to 200 μm constituting the composition of the polyester layer (A), a thermoplastic resin other than polyester, and an average particle size of 0.5 to 20.
Additives such as 0 μm spherical particles are added in a total amount of 0.1 at the time of polyester synthesis or extrusion kneading in film formation.
~ 30 parts by weight are added. Similarly, additives such as inert particles constituting the composition of the polyester layer (B) are also added in an amount of 0.01 to 5 parts by weight during the synthesis of polyester or during extrusion kneading during film formation.

First, the polyester chip forming the A layer and the polyester chip forming the B layer are each dried, and each is heated at a normal extrusion temperature in a dedicated extruder.
That is, the melting point (hereinafter referred to as Tm) or more, (Tm + 7
The mixture is melt-kneaded at a temperature of 0 ° C. or less, and is laminated by, for example, a feed block in the die to form a laminated unstretched film by a simultaneous multilayer extrusion method. Here, the feed block needs to be designed in a laminated structure composed of B / A, and the molten material laminated in the feed block maintains its form. The laminated molten film extruded from the die is cooled and solidified by a casting drum to obtain a laminated unstretched film. In order to improve the adhesion between the film-like melt and the casting drum in this step,
It is preferable to use an electrostatic adhesion method for imparting an electrostatic charge to the film-like melt.

The unstretched film thus obtained is heated by roll heating, infrared heating or the like, and stretched in the longitudinal direction to obtain a longitudinally stretched film. This stretching is preferably performed by utilizing the peripheral speed difference between two or more rolls. The stretching temperature is higher than the glass transition temperature of polyester (hereinafter referred to as Tg), and further, (Tg + 20) to (Tg +).
The temperature is preferably 40) ° C., and the draw ratio is preferably 2.0 times or more and 4.0 times or less, although it depends on the required characteristics of this application. Draw ratio is 2.5 times or more 4.
It is more preferably 0 times or less and 2.8 times or more.
It is more preferably 9 times or less. Stretch ratio is 2.
When it is less than 0 times, it is difficult to obtain a good film because the thickness unevenness of the polyester film becomes large. If the draw ratio is less than 2.0 times, the stress applied to the thermoplastic resin other than the plate-like filler or polyester during drawing is not sufficient, so the orientation angle of the plate-like filler and the shape factor of the thermoplastic resin other than polyester Is not required,
The visibility of reflected light is low. On the other hand, the draw ratio is 4.
If it exceeds 0 times, breakage tends to occur during film formation.

The longitudinally stretched film thus obtained is then sequentially subjected to the treatment steps of transverse stretching, heat setting and heat relaxation to obtain a biaxially oriented film. These treatments are carried out while the film is running. The transverse stretching treatment is started at a temperature 20 ° C. higher than the glass transition point (Tg) of the thermoplastic resin, and is raised to a temperature (120 to 30) ° C. lower than the melting point (Tm) of the thermoplastic resin. This transverse stretching start temperature is (Tg + 20)
It is more preferable that the temperature is not less than 0 ° C and not more than (Tg + 40) ° C. Also, the maximum transverse stretching temperature is from Tm (100 to 40)
It is more preferable that the temperature is lower by 0 ° C.

The temperature rise in the transverse stretching process may be continuous or stepwise (sequential). Usually, the temperature is raised sequentially. For example, the transverse stretching zone of the stenter is divided into a plurality along the film traveling direction, and the temperature is raised by flowing a heating medium of a predetermined temperature in each zone. If the transverse stretching start temperature is lower than (Tg + 20) ° C., the film is easily broken, which is not preferable. If the maximum transverse stretching temperature is lower than (Tm-120) ° C, the heat shrinkage of the film becomes large and the uniformity of the physical properties in the width direction is deteriorated, which is not preferable. On the other hand, when the maximum transverse stretching temperature is higher than (Tm-30) ° C, the film becomes too soft, and the film is torn due to external factors such as the film take-up speed, which is not preferable.

The transverse stretching ratio is preferably 2.0 times or more and 4.0 times or less, though it depends on the characteristics required for this application. It is more preferably 2.5 times or more and 4.0 times or less, and further preferably 2.8 times or more and 3.9 times or less. 2.0
If it is less than twice, it is difficult to obtain a good film because the thickness unevenness of the film becomes large, and if it exceeds 4.0 times, breakage easily occurs during film formation.

After transverse stretching, a heat setting treatment is subsequently carried out. A preferable heat setting temperature range is (Tg + 70) to
(Tm-10) ° C. For example, in the case of polyethylene terephthalate, 180 to 235 ° C., polyethylene-2,
In the case of 6-naphthalate, 220 to 240 ° C. is exemplified as a preferable heat setting temperature condition. The heat setting time is preferably 1 to 60 seconds. Further, for applications that require a reduction in the heat shrinkage rate, a heat relaxation treatment may be performed if necessary.

Thus, the plate-like filler has a thickness of 3 to 250 μm, an intrinsic viscosity of 0.40 to 1.50 dl / g, and is oriented in the plane direction of the polyester film at an orientation angle of 30 ° or less. Resin has a shape factor of 2
A transflective laminated polyester film as described above is obtained.

The semi-transmissive reflective laminated polyester film of the present invention obtained by the above method preferably has high transparency in order to ensure good visibility, and specifically, has a visible light transmittance of 90% or more. It is preferable that the haze is 5% or less. If the visible light transmittance is less than 90% or the haze is more than 5%, the transparency is poor and sufficient visibility cannot be obtained with transmitted light.

In the present invention, an adhesive layer may be further provided on at least one surface of the transflective laminated polyester film. When the outermost layer of the transflective laminated polyester film is composed of the B layer on both sides, the adhesive layer may be formed on either side. When the outermost layer of the transflective laminated polyester film is formed of the A layer and the B layer, the adhesive layer may be formed on either surface, but it is more preferably on the B surface.

The pressure-sensitive adhesive layer may be applied to a polyester film by a known coating method. Alternatively, after the pressure-sensitive adhesive layer is formed on the release film in advance by a known coating method, one side of the polyester film is coated. Alternatively, a method may be used in which the adhesive layer is adhered on the upper surface, the release film is then peeled off, and the adhesive layer is transferred onto one surface of the transflective laminated polyester film. Further, the adhesive layer is applied to the polarizing film by a known coating method,
The transflective laminated polyester film and the polarizing film may be attached together. In the final stage of use as a product, the transflective laminated polyester film and the polarizing film are laminated via the adhesive layer.

The adhesive layer can be applied by any known coating method. For example, kiss coating method, bar coating method, die coating method, reverse coating method, offset gravure coating method, Myer bar coating method, gravure coating method, roll brush method, spray coating method, air knife coating method, impregnation method and curtain coating method, etc. May be applied alone or in combination.

In the present invention, if necessary, a hard coat layer may be further provided on one surface of the transflective laminated polyester film. Such a hard coat layer is preferably formed on the side opposite to the adhesive layer via a polyester film, and is preferably positioned as the outermost layer when used as a product.

The hard coat layer is applied to a polyester film by a known coating method and cured. Any known coating method can be applied to the coating of the hard coat layer. For example, kiss coat method, bar coat method, die coat method, reverse coat method, offset gravure coat method,
The Mayer bar coating method, the gravure coating method, the roll brush method, the spray coating method, the air knife coating method, the impregnation method, the curtain coating method and the like may be applied alone or in combination.

[0077]

EXAMPLES The present invention will be further described below with reference to examples. Each characteristic value was measured by the following method. 1. Orientation angle of plate-like filler An arbitrary cross section of the obtained transflective laminated polyester film was taken with a scanning electron microscope (JSM, JSM-
5200), the image was taken at a magnification of 1000 to 5000 times, and for any 100 plate-like fillers, the orientation angle of the flat surface of the filler with respect to the polyester film surface was measured to calculate the average value. 2. Shape Factor of Thermoplastic Resin Dispersed Phase Other Than Polyester An arbitrary cross section of the obtained transflective laminated polyester film is taken by a scanning electron microscope (manufactured by JEOL Ltd., JSM-
5200) and magnified 1000 to 5000 times and photographed about 100 arbitrary thermoplastic resin dispersed phases,
The major axis / minor axis in the cross section was measured with an image analyzer, and the shape factor was determined from the average value. 3. Total light transmittance and total light reflectance UV / visible spectrophotometer (manufactured by Shimadzu Corporation, UV-3101)
The total light transmittance and the total light reflectance at 550 nm of the obtained transflective laminated polyester film were measured using PC). 4. Solvent resistance The obtained transflective laminated polyester film was immersed in methyl ethyl ketone for 24 hours, and the appearance of the film after immersion was observed and evaluated according to the following criteria. ◯: No visual change in film appearance Δ: Visually slightly whitened film appearance ×: Visually markedly changed whitening or peeling of film appearance 5. Film-forming stability The film-forming conditions in the film-forming process of the transflective laminated polyester film were evaluated according to the following criteria. ◯: A film can be formed in a very stable state without breakage. Δ: A film can be formed although breakage sometimes occurs. X: Breakage occurs frequently, and no film can be formed.

Example 1 As a polyester layer (A), a melting point of 228 ° C. obtained by copolymerizing 12 mol% of isophthalic acid.
Polyethylene terephthalate (Intrinsic viscosity: 0.64d
l / g, Tg: 75 ° C) 95% by weight, average major axis 15μ
m pearl pigment (Merck, product name "IRIODIN
111 ") and 5% by weight, and melting point 228 obtained by copolymerizing 12 mol% of isophthalic acid as the polyester layer (B).
℃ polyethylene terephthalate (intrinsic viscosity: 0.64
dl / g, Tg: 75 ° C.) 99.9% by weight and agglomerated silica particles having an average particle size of 1.5 μm 0.1% by weight,
Both the A and B layers were melt-kneaded at 280 ° C., the A / B two-layer structure was adjusted so that the A / B thickness ratio was 4/1, and rapidly solidified to obtain an unstretched film of 533 μm. The unstretched film is heated to 110 ° C. and stretched in the machine direction by a factor of 3.6,
Next, the longitudinally stretched film heated to 120 ° C. was stretched in the transverse direction 3.9 times. After that, heat setting treatment was performed at a heat setting temperature of 185 ° C. for 20 seconds to obtain a biaxially oriented film having a thickness of 40 μm. The properties of the obtained transflective laminated polyester film are shown in Table 1.

Example 2 As the polyester layer (A), a melting point of 228 ° C. obtained by copolymerizing 12 mol% of isophthalic acid.
Polyethylene terephthalate (Intrinsic viscosity: 0.64d
l / g, Tg: 75 ° C) 95% by weight, average major axis 15μ
m pearl pigment (Merck, product name "IRIODIN
111 ") and 5% by weight, and melting point 228 obtained by copolymerizing 12 mol% of isophthalic acid as the polyester layer (B).
℃ polyethylene terephthalate (intrinsic viscosity: 0.64
dl / g, Tg: 75 ° C.) 99.9% by weight and agglomerated silica particles having an average particle size of 1.5 μm 0.1% by weight,
Both A and B layers were melt-kneaded at 280 ° C., adjusted to have a B / A / B thickness ratio of 0.5 / 4 / 0.5 with a three-layer structure of B / A / B, and rapidly solidified. An unstretched film of 533 μm was obtained. The unstretched film was heated to 110 ° C. and stretched in the longitudinal direction by 3.6 times, and then the longitudinally stretched film heated to 120 ° C. was stretched in the transverse direction by 3.9 times. Then 1
A heat setting treatment was performed at a heat setting temperature of 85 ° C. for 20 seconds to obtain a biaxially oriented stretched film having a thickness of 40 μm. The properties of the obtained transflective laminated polyester film are shown in Table 1.

Example 3 Polyethylene terephthalate having a melting point of 260 ° C. (intrinsic viscosity: as polyester for forming the polyester layer (A) and the polyester layer (B))
0.64 dl / g, Tg: 78 ° C.) was used, and a film was formed under the same conditions as in Example 1 except that the longitudinal stretching ratio was 3.4 times and the transverse stretching ratio was 3.6 times. The properties of the obtained transflective laminated polyester film are shown in Table 1.

Example 4 As the polyester layer (B), a melting point of 228 ° C. obtained by copolymerizing 12 mol% of isophthalic acid.
Polyethylene terephthalate (Intrinsic viscosity: 0.64d
99/85% by weight, agglomerated silica particles having an average particle size of 1.5 μm, and 0.1% by weight, and an optical brightener (“OB-1” manufactured by Eastman Co., Ltd.). ) 0.0
A film was formed under the same conditions as in Example 1 except that 5% by weight was used. The properties of the obtained transflective laminated polyester film are shown in Table 1.

Example 5 As the polyester layer (A), 97% by weight of polyethylene terephthalate having a melting point of 260 ° C. (intrinsic viscosity: 0.64 dl / g, Tg: 78 ° C.)
And 3% by weight of poly-4-methyl-1-pentene resin (“TPX-DX820” manufactured by Mitsui Petrochemical Co., Ltd.) were dried at 140 ° C. for 6 hours. On the other hand, as the polyester layer (B), polyethylene terephthalate having a melting point of 260 ° C. (intrinsic viscosity: 0.64 dl / g, Tg: 78 ° C.) 9
Using 9.9% by weight and 0.1% by weight of agglomerated silica particles having an average particle size of 1.5 μm, the resin composition for both the A layer and the B layer was melt-kneaded at 280 ° C. to obtain 2 layers of A / B. A / B in configuration
Adjust the thickness ratio to 4/1, then quench and solidify to 560
An unstretched film of μm was obtained. 11 of the unstretched film
Heat to 0 ° C and stretch in the machine direction 3.0 times, then
The longitudinally stretched film heated to 0 ° C. was stretched 3.1 times in the transverse direction. After that, heat setting treatment was performed at a temperature of 185 ° C. for 20 seconds to obtain a biaxially oriented film having a thickness of 60 μm. The properties of the obtained transflective laminated polyester film are shown in Table 1.

Example 6 99.0% by weight of polyethylene terephthalate having a melting point of 260 ° C. (intrinsic viscosity: 0.64 dl / g, Tg: 78 ° C.) as the polyester layer (B)
And 1.0% by weight of agglomerated silica particles having an average particle size of 4.0 μm
A film was formed under the same conditions as in Example 1 except that was used. The properties of the obtained transflective laminated polyester film are shown in Table 1.
Shown in.

[Comparative Example 1] 60 parts by weight of a polyester resin (manufactured by Hitachi Chemical Co., Ltd., product name "ESPER 1510", used as a binder for a semi-transmissive reflective layer) and a pearl pigment having an average major axis of 20 µm (Merck, product name) "IRI
ODIN 123 ") 40 parts by weight of methyl ethyl ketone was added and dispersed, and then 5 parts of methyl ethyl ketone was added.
A mixed solvent of 0 parts by weight and 50 parts by weight of toluene was added to adjust the viscosity of the solution to 200 mPas to prepare a semi-transmissive reflective layer forming coating solution. This coating solution is a biaxially stretched polyethylene terephthalate film (manufactured by Teijin DuPont Films Ltd.,
A product name “Tetoron” film, G2-38 μm thick) was coated on one side with a comma coater and dried at 130 ° C. for 1 minute to obtain a semi-transmissive reflective film having a semi-transmissive reflective layer having a thickness of 8 μm. At this time, the ratio of the average major axis of the pearl pigment in the semi-transmissive reflective layer to the thickness of the layer after drying was 2.5. The properties of the obtained semi-transmissive reflective film are shown in Table 1.

[Comparative Example 2] 97% by weight of polyethylene terephthalate (intrinsic viscosity: 0.64 dl / g, Tg: 75 ° C) having a melting point of 228 ° C obtained by copolymerizing 12 mol% of isophthalic acid, and a pearl pigment having an average major axis of 15 µm ( Made by Merck, product name "IRIODIN 111") 3% by weight,
It was melt-kneaded at 280 ° C. and rapidly solidified to obtain an unstretched film of 533 μm. The unstretched film was heated to 110 ° C. and stretched in the longitudinal direction by 3.6 times, and then the longitudinally stretched film heated to 120 ° C. was stretched in the transverse direction by 3.9 times.
After that, heat setting treatment was performed at a heat setting temperature of 185 ° C. for 20 seconds to obtain a biaxially oriented film having a thickness of 40 μm. The properties of the obtained semi-transmissive reflective polyester film are shown in Table 1.

[Comparative Example 3] As the polyester layer (A), a melting point of 228 ° C. obtained by copolymerizing 12 mol% of isophthalic acid.
Polyethylene terephthalate (Intrinsic viscosity: 0.64d
l / g, Tg: 75 ° C) 95% by weight, average major axis 15μ
m pearl pigment (Merck, product name "IRIODIN
111 ") and 5% by weight, and melting point 228 obtained by copolymerizing 12 mol% of isophthalic acid as the polyester layer (B).
℃ polyethylene terephthalate (intrinsic viscosity: 0.64
dl / g, Tg: 75 ° C.) 99.9% by weight and agglomerated silica particles having an average particle size of 1.5 μm 0.1% by weight,
Both the A and B layers were melt-kneaded at 280 ° C., the A / B two-layer structure was adjusted so that the A / B thickness ratio was 4/1, and the mixture was rapidly solidified to obtain an unstretched film having a thickness of 40 μm. The properties of the obtained laminated unstretched film are shown in Table 1.

[Comparative Example 4] Under the same conditions as in Example 1 except that the content of isophthalic acid copolymerized polyethylene terephthalate in the polyester layer (A) was 65% by weight and the content of pearl pigment was 35% by weight. Although a film was formed, the film was not able to be formed due to frequent breakage.

[0088]

[Table 1]

As shown in Table 1, in each of the transflective laminated polyester films of Examples 1 to 4 and Example 6, the average major axis of the pearl pigment, which is a plate-like filler, the addition amount, and the polyester film formation As a result of proper stretching conditions, the pearl pigment is oriented at an orientation angle of 30 ° or less with respect to the plane direction of the polyester film, and the total light transmittance and the total light reflectance of the obtained transflective laminated polyester film are required. The characteristics were satisfied, and the visibility of transmitted light and the visibility of reflected light were good. Also, it has excellent solvent resistance,
Further, by stacking the polyester layer (B) containing an inert particle having an appropriate particle size and addition amount, the film forming stability was better than that of Comparative Example 2 including only the polyester layer (A). .

Similarly, in the transflective laminated polyester film of Example 5, the addition amount of poly-4-methyl-1-pentene resin, which is a thermoplastic resin other than polyester, and the stretching conditions when forming the polyester film are appropriate. As a result, the shape factor was 2 or more, the total light transmittance and the total light reflectance of the obtained semi-transmissive reflective laminated polyester film satisfied the required characteristics, and both the transmitted light visibility and the reflected light visibility were good. there were. Further, as compared with Comparative Example 2 including only the polyester layer (A), the polyester layer (B) which has excellent solvent resistance and further contains an inert particle with an appropriate particle diameter and an appropriate amount is laminated. The film forming stability was good.

On the other hand, Comparative Example 1 was produced by a conventional method for producing a semi-transmissive reflective film, which was produced by coating a semi-transmissive reflective layer on a film substrate. When the obtained semi-transmissive reflective film was immersed in methyl ethyl ketone for 24 hours and the solvent resistance was evaluated, the coating layer was peeled from the film substrate and the solvent resistance was insufficient. Further, in Comparative Example 2, inactive particles having an average particle diameter of 0.01 to 5 μm are added to 0.0
As a result of not laminating the polyester layer (B) containing 1 to 5% by weight, the film forming stability was poor. In Comparative Example 3, although the average major axis of the pearl pigment as the plate-like filler and the addition amount were sufficient, the pearl pigment was not oriented at 30 ° or less with respect to the plane direction of the polyester film as a result of not performing stretching. The total light reflectance of the obtained transflective laminated polyester film was less than 40%, and the visibility of reflected light was deteriorated. In Comparative Example 4, the amount of the pearl pigment added was more than 30% by weight, the film was frequently broken during film formation, and film formation was not achieved.

[0092]

The semi-transmissive reflective laminated polyester film obtained by the present invention has good visibility in transmitted light using the backlight of the liquid crystal display as a light source, and at the same time, reflects and diffuses visible light. By using a method of containing the agent in a state of being arranged in the film base material so that the agent exhibits its characteristics, the visibility of the liquid crystal display in both transmitted light and reflected light is excellent, and the liquid crystal display member and It is possible to provide a semi-transmissive reflective laminated polyester film having high film-forming stability and suitable for liquid crystal display by improving the time-dependent adhesion with the transmissive reflective laminated polyester film and forming a laminated structure.

Front page continuation (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) // G02F 1/13357 G02B 1/10 Z (72) Inventor Keita Takehisa 3 37-19 Oyama, Sagamihara City, Kanagawa People DuPont Films Co., Ltd. Sagamihara Research Center (72) Inventor Tetsuo Ichihashi 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin DuPont Films Co., Ltd. Sagamihara Research Center F-term (reference) 2H042 BA02 BA12 BA20 2H091 FA16Z FB02 FB13 FC08 FC29 FD07 FD23 LA03 LA11 LA18 2K009 AA15 BB24 CC24 DD05 4F100 AA20A AA20H AK01A AK03A AK08A AK41A AK41B AK42 AL05A AL05B AR00C BA02 BA03 BA07 BA10A BA10B BA10C BA44 CA13 CA23 DE01A DE01B DE10A EH20 EH202 EJ37A EJ37B EJ38 EJ382 EJ42 EJ422 GB41 JA20A JB16A JK12C JN01 JN02 JN08 JN21A YY00A YY00B

Claims (8)

[Claims] 1. A laminated polyester film comprising at least two layers, which comprises a polyester layer (A) and a polyester layer (B) and is stretched in at least one axis direction, and has a total light reflectance at a wavelength of 550 nm of at least 40%. As described above, the total light transmittance at the above wavelength is at least 20% or more, and the sum of the above total light reflectance and the total light transmittance is 80% or more, and the polyester layer (A).
Is oriented at an orientation angle of 30 ° or less in the plane direction of the polyester film in the layers (a) and (A).
Either a 200 μm plate-like filler, (b) a dispersed phase of a thermoplastic resin other than polyester having a shape factor of 2 or more in the (A) layer, or (c) spherical particles having an average particle size of 0.5 to 200 μm. 0.1 to 30 in total with respect to the layer (A)
% By weight, and the polyester layer (B) has an average particle size of 0.
0.01 to 5 μm of inert particles with respect to the layer (B) is 0.01
A transflective laminated polyester film, characterized in that the transflective laminated polyester film contains 5 to 5% by weight. 2. The transflective laminated polyester film according to claim 1, wherein the plate-like filler is a pearl pigment. 3. The transflective laminated polyester film according to claim 1, wherein the thermoplastic resin other than polyester is a polyolefin resin. 4. The polyolefin resin is poly-4-methyl-
It is 1-pentene resin, The transflective laminated polyester film of Claim 3 characterized by the above-mentioned. 5. The transflective laminated polyester film according to claim 1, wherein the spherical particles are titanium oxide and / or calcium carbonate. 6. The transflective laminated polyester film according to claim 1, which has an adhesive layer on at least one surface of the polyester film. 7. A hard coat layer is provided on at least one surface of a polyester film.
The transflective laminated polyester film according to any one of 1 to 6. 8. (a) An average major axis of 0.5 to 200 μm,
And a plate-like filler that is oriented by an orientation angle of 30 ° or less in the plane direction of the film by stretching, and (b) a thermoplastic resin other than polyester that has a shape factor of 2 or more in the polyester layer (A) by stretching. Or (c) a polyester layer (A) containing a total of 0.1 to 30% by weight of spherical particles having an average particle size of 0.5 to 200 μm with respect to the (A) layer, and an average particle size of 0. A laminated unstretched polyester film composed of a polyester layer (B) containing 0.01 to 5 μm of inert particles in an amount of 0.01 to 5% by weight based on the layer (B) was drawn at a draw ratio of 2.0 to 4.0. A method for producing a transflective laminated polyester film, comprising obtaining the polyester film having transflective characteristics according to claim 1 by stretching in at least a uniaxial direction.