JP2022117511A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thinner liquid crystal display device that prevents the generation of an iridescent speckle and the warp of a liquid crystal panel.

SOLUTION: A liquid crystal display device includes a backlight source, a light source-side polarizing plate, a liquid crystal cell, and a viewing-side polarizing plate in this order. The light source-side polarizing plate and the viewing-side polarizing plate each include at least one polarizer protective film and a polarizer. When the polarizer protective film of the viewing-side polarizing plate and located on a surface opposite to the liquid crystal cell of the polarizer is referred to as a polarizer protective film 1 and the polarizer protective film of the light source-side polarizing plate and located on the surface opposite to the liquid crystal cell of the polarizer is referred to as a polarizer protective film 4, in-plane retardation of the polarizer protective film 4 is 5,000-10,000 nm, and a ratio of in-plane retardation of the polarizer protective film 1/in-plane retardation of the polarizer protective film 4 is 0.55-0.95.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that can be made thinner while suppressing deterioration in visibility due to warping of a liquid crystal panel and iridescence.

In recent years, image display devices are required to be larger and thinner. Along with this, in the liquid crystal display device as well, the problem that the liquid crystal cell warps concavely in the long side direction when viewed from the viewing side during use and causes light leakage at the corners has come to the surface. In addition, for polarizing plates used in liquid crystal display devices, high-retardation polarizer protective films have been proposed and are becoming widespread. However, it was necessary to ensure a high retardation, and there were restrictions on reducing the thickness of the film. In particular, the iridescence becomes more visible as it tilts diagonally from the front, but as the retardation decreases, the angle at which the iridescence does not stand out sharply narrows.

Moreover, as a method for reducing the warp of the liquid crystal panel, a method of adjusting the shrinkage force in the width direction (TD) of the polarizer protective film of the light source side polarizing plate has been proposed (for example, Patent Document 1).

On the other hand, liquid crystal display devices generally have a structure in which polarizing plates are attached to both sides of a liquid crystal cell. A polarizing plate having the same thickness and optical properties has been used except that an antireflection layer, an antiglare layer, and the like are provided on the viewing side polarizer protective film of the side polarizing plate.

WO2019/054406

An object of the present invention is to provide a thinner liquid crystal display device while preventing iridescence from occurring.
The present inventors found that the warping of the liquid crystal panel is greatly affected by the contraction of the polarizer of the viewing side polarizing plate, and when the thickness of the polarizer protective film is reduced, the force of the polarizer protective film to resist the contraction of the polarizer is also weakened. , it was found that the liquid crystal panel tends to warp. Another object of the present invention is to provide a thinner liquid crystal display device while preventing the liquid crystal panel from warping.

The present invention includes the following aspects.
Section 1. In a liquid crystal display device comprising a backlight source, a light source side polarizing plate, a liquid crystal cell, and a viewing side polarizing plate in this order, each of the light source side polarizing plate and the viewing side polarizing plate has at least one polarizer protective film and a polarizer. Then, the polarizer protective film of the viewing side polarizing plate and located on the opposite side of the polarizer to the liquid crystal cell is called polarizer protective film 1, and the polarizer protective film of the light source side polarizing plate and polarized light When the polarizer protective film located on the opposite side of the liquid crystal cell of the element is the polarizer protective film 4, the in-plane retardation of the polarizer protective film 4 is 5000 to 10000 nm, and the in-plane retardation of the polarizer protective film 1 is / A liquid crystal display device in which the in-plane retardation ratio of the polarizer protective film 4 is from 0.55 to 0.97.

Section 2. Item 2. The liquid crystal display device according to item 1, wherein the in-plane retardation of the polarizer protective film 1 is 4500 to 9500 nm.

Item 3. Item 3. The liquid crystal display device according to Item 1 or 2, wherein the ratio of the in-plane retardation of the polarizer protective film 1/the in-plane retardation of the polarizer protective film 4 is 0.55 to 0.95.

Section 4. 4. The method according to any one of Items 1 to 3, wherein the thickness of the polarizer protective film 4 is 50 to 95 μm, and the ratio of the thickness of the polarizer protective film 1/the thickness of the polarizer protective film 4 is 0.5 to 0.97. liquid crystal display.

Item 5. Item 5. The liquid crystal display device according to any one of Items 1 to 4, wherein the thickness of the polarizer protective film 1 is 40 to 80 µm.

Item 6. Item 6. The liquid crystal display device according to any one of Items 1 to 5, wherein the ratio of the thickness of the polarizer protective film 1/the thickness of the polarizer protective film 4 is 0.5 to 0.95.

With the above configuration, for example, it is possible to provide a thinner liquid crystal display device while preventing iridescence, and to provide a thinner liquid crystal display device while preventing warping of the liquid crystal panel.

The inventors of the present invention have made intensive studies on the occurrence of iris spots and warping of liquid crystal panels and methods for suppressing them, and have clarified the following, and have found a method for suppressing iris spots and warping while realizing thinness. The discovery and further investigations led to the present invention.
- In the case of a polarizing plate using a polarizer protective film with high retardation, rainbow spots are more visible when the polarizing plate is used on the light source side than when the polarizing plate is used on the viewing side.
- When the polarizer protective film of the light source side polarizing plate and the viewer side polarizing plate have the same retardation, the retardation of the polarizer protective film of the viewer side polarizing plate must be excessive.
• It is possible to reduce the thickness of the display device by eliminating the excess retardation of the polarizer protective film of the viewing side polarizing plate.
・In order to suppress warping of the liquid crystal panel, the strength of the polarizer protective film on the opposite side of the polarizing plate on the light source side from the liquid crystal cell is important.

The liquid crystal display device of the present invention includes a backlight source, a light source side polarizing plate, a liquid crystal cell, and a viewing side polarizing plate in this order. In this specification, the term “liquid crystal panel” refers to a liquid crystal cell in which a liquid crystal compound is enclosed between two substrates, and a polarizing plate arranged (or bonded) on each of the light source side and the viewing side of the liquid crystal cell. Say. Accordingly, the liquid crystal display device of the present invention has a backlight source and a liquid crystal panel. The polarizing plate has a polarizer and at least one polarizer protective film, and the polarizer protective film is arranged (or attached) on the opposite side of the polarizer to the liquid crystal cell. Furthermore, another film or layer (polarizer protective film, retardation film, cured resin layer, etc.) may be provided on the liquid crystal cell side of the polarizer, and the polarizer may be directly bonded to the liquid crystal cell. good.

In this specification, a liquid crystal panel may be simply called a panel, and a liquid crystal cell may be simply called a cell. Further, the polarizer protective film on the side opposite to the liquid crystal cell of the viewing side polarizing plate is the polarizer protective film 1, the polarizer protective film or retardation film on the liquid crystal cell side of the viewing side polarizing plate is the polarizer protective film 2, and the light source The polarizer protective film or retardation film on the liquid crystal cell side of the side polarizing plate is sometimes called polarizer protective film 3, and the polarizer protective film on the side opposite to the liquid crystal cell of the light source side polarizing plate is sometimes called polarizer protective film 4. .

The properties of the polarizer protective film 1 and the polarizer protective film 4 are described below. Unless otherwise specified, the polarizer protective film 1 and the polarizer protective film 4 refer to base films having no functional layer or the like, which will be described later. In addition, the base film may contain the easy-adhesion layer mentioned later.

The lower limit of the in-plane retardation (hereinafter sometimes referred to as Re or retardation) of the polarizer protective film 4 is preferably 5000 nm, more preferably 5500 nm, still more preferably 6000 nm. By setting the angle above the above, it is possible to secure a wide angle at which the rainbow spot is not conspicuous.
The upper limit of Re of the polarizer protective film 4 is preferably 10000 nm, more preferably 9500 nm, still more preferably 9000 nm, and particularly preferably 8700 nm. By setting the thickness to be less than or equal to the above, the excess thickness is reduced, and it becomes easy to make the display device thinner.
Re is the in-plane retardation of the film, and is obtained by multiplying the difference between the refractive indices nx and ny of the two orthogonal axes when viewed from the plane of the film by the thickness d of the film. The refractive index can be determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measuring wavelength 589 nm).

The lower limit of Re of the polarizer protective film 1 is preferably 4500 nm, more preferably 5000 nm, still more preferably 5500 nm. By setting the angle above the above, it is possible to secure a wide angle at which the rainbow spot is not conspicuous.
The upper limit of Re of the polarizer protective film 1 is preferably 9500 nm, more preferably 9000 nm, still more preferably 8500 nm, particularly preferably 8000 nm, most preferably 7500 nm. By setting the thickness to be less than or equal to the above, the excess thickness is reduced, and it becomes easy to make the display device thinner.

The lower limit of the ratio of the in-plane retardation of the polarizer protective film 1/the in-plane retardation of the polarizer protective film 4 (sometimes simply referred to as the Re ratio) is preferably 0.55, more preferably 0.6, It is more preferably 0.65, and particularly preferably 0.7.
The upper limit of the Re ratio is preferably 0.97, more preferably 0.96, still more preferably 0.95. In addition, particularly preferred upper limits are 0.9, 0.85, or 0.8. By setting the thickness to be less than or equal to the above, the excess thickness is reduced, and it becomes easy to make the display device thinner.

In order to obtain the effects of the present invention while the polarizer protective films 1 and 4 have similar optical properties, it is also a preferred embodiment that the Re ratio is more than 0.95 and 0.97 or less.

Regarding the range of the Re ratio, rainbow spots are more conspicuous when a film with a high retardation is used as the polarizer protective film 4 than when the polarizer protective film 1 is used. This is based on the knowledge that the range in which the rainbow spots are not conspicuous is narrower when used for the polarizer protective film 4 . That is, the polarizer protective film 1 on the viewing side polarizing plate may have a lower retardation as long as the rainbow spots are not conspicuous. In other words, when the polarizer protective film 1 and the polarizer protective film 4 are films with the same retardation, the rainbow spots are strongly influenced by the polarizer protective film 4, and excessive retardation may occur in the polarizer protective film 1. . It should be noted that the term "inconspicuous iridescence" as used herein also includes the case where iridescence is not observed.

In addition, in liquid crystal display devices such as televisions, especially VA type and IPS type liquid crystal display devices, in order to prevent blackout when viewed with polarized sunglasses, the absorption axis of the polarizer of the viewing side polarizing plate The direction is often horizontal. Furthermore, general polarizers are stretched in the machine direction (MD) of film formation, and the MD direction becomes the absorption axis. is the main orientation axis in many cases, and as a result, in the polarizing plate, the absorption axis direction of the polarizer and the main orientation axis direction of the high-retardation polarizer protective film are often orthogonal to each other. Therefore, in many cases, the main alignment axis of the polarizer protective film 1 is the vertical direction of the liquid crystal display device, and the main alignment axis of the polarizer protective film 4 is the horizontal direction of the liquid crystal display device. Furthermore, in the general liquid crystal display device described above, the long side direction is often the horizontal direction.

On the other hand, the iridescence produced by a high retardation film is less likely to occur when observed with an inclination from the normal direction of the film to the main orientation axis direction or the orthogonal direction of the film, and is 20 to 20 degrees from the main orientation axis direction of the film Iridescent spots are more likely to occur when observed in a direction shifted by about 50 degrees, that is, when observed slightly tilted toward the direction of the main orientation axis. In general, when viewing a liquid crystal display screen, it is often viewed at an angle in the horizontal direction (left and right) rather than viewed at an angle in the vertical direction (up and down). For this reason, in order to reduce the thickness, it is preferable to give priority to reduction of iridescence occurring in the polarizer protective film 4 of the light source side polarizing plate.

The reason why the polarizer protective film 4 on the light source side polarizing plate produces stronger rainbow spots is that a reflective polarizing plate is often used between the light source and the polarizer protective film 4 to improve brightness. Linearly polarized light is incident on the protective film 4, and reflection at the surface interface of the polarizer protective film 4 generates a polarized component. is clarified by the polarizer of the light source side polarizing plate, and the surface of the polarizer protective film 1 of the viewing side polarizing plate is often provided with an antireflection layer or an antiglare layer, so that rainbow spots are more likely to be suppressed. However, the present invention is not limited by any reason.

The lower limit of the thickness direction retardation (Rth) of the polarizer protective film 4 is preferably 5200 nm, more preferably 5500 nm, even more preferably 5700 nm, even more preferably 6000 nm, and particularly preferably 6200 nm. The upper limit of Rth of the polarizer protective film 4 is preferably 12000 nm, more preferably 11000 nm, still more preferably 10000 nm, and particularly preferably 9500 nm.

The lower limit of Rth of the polarizer protective film 1 is preferably 4700 nm, more preferably 5000 nm, still more preferably 5200 nm, still more preferably 5500 nm, and particularly preferably 5700 nm. The upper limit of Rth of the polarizer protective film 1 is preferably 10000 nm, more preferably 9500 nm, even more preferably 9000 nm, still more preferably 8500 nm, and particularly preferably 8000 nm.

The retardation in the thickness direction is obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) when viewed from the cross section in the thickness direction of the film by the film thickness d. It is the average value of retardation.

The polarizer protective films 1 and 4 each independently have a lower limit of Re/Rth of preferably 0.8, more preferably 0.85, still more preferably 0.9. Polarizer protective films 1 and 4 each independently have an upper limit of Re/Rth of preferably 1.2, more preferably 1.1, still more preferably 1.05, and particularly preferably 1. . The larger the Re/Rth, the wider the range of angles in which the iridescence is not conspicuous. Re/Rth is 2 for a perfect uniaxial (uniaxially symmetrical) film, but as the value becomes farther from 2, the mechanical strength in the direction perpendicular to the orientation direction improves, the film is less likely to break, and productivity increases. tend to improve.

Polarizer protective films 1 and 4 each independently have a lower limit of the NZ coefficient of preferably 1.4, more preferably 1.45, still more preferably 1.47. By doing more than the above, it becomes easier to produce stably. The upper limit of the NZ coefficient of each of the polarizer protective films 1 and 4 is preferably 1.7, more preferably 1.68, and even more preferably 1.66.
The smaller the NZ coefficient, the wider the range of angles in which the iridescence is less conspicuous. A perfect uniaxial (uniaxially symmetrical) film has a NZ coefficient of 1.0. tend to improve.
The NZ coefficient is NZ=|nx−nz|/|nx−ny|, and is obtained by substituting nx, ny, and nz of the film into the formula.

Appropriate ranges of the above-mentioned Re, Rth, Re/Rth, and NZ coefficients, particularly the lower limits of Re, Rth, and NZ coefficients related to the width of the field of view, and the upper limits of Re/Rth, depend on the application of the liquid crystal display device. A suitable range can be selected. For example, a wide viewing angle is preferable for televisions and digital signage applications, but for example, in car navigation systems, back and side monitors of mirrorless automobiles, personal computer monitors, ATM screens, smartphones, etc., even if the viewing angle is narrow, the viewing angle is large. There may be no problems. Therefore, the effect of the present invention is not necessarily that a wide viewing angle is preferable in all cases, but that it is possible to make the display thinner while securing the viewing angle necessary for the application.

The lower limit of the thickness of the polarizer protective film 4 (the polarizer protective film on the side of the polarizing plate on the light source side opposite to the liquid crystal cell) is preferably 50 μm, more preferably 55 μm, and still more preferably 60 μm. When the thickness is above the above, it becomes easy to suppress the warp of the liquid crystal panel, and it becomes easy to secure the retardation for suppressing the occurrence of iridescence.
The upper limit of the thickness of the polarizer protective film 4 is preferably 95 μm, more preferably 90 μm, still more preferably 85 μm. By setting the thickness below the above range, it becomes easier to make the display device thinner.

The lower limit of the thickness of the polarizer protective film 1 (the polarizer protective film on the viewer side polarizing plate opposite to the liquid crystal cell) is preferably 40 μm, more preferably 45 μm, and still more preferably 50 μm. When the thickness is above the above, it becomes easy to suppress the warp of the liquid crystal panel, and it becomes easy to secure the retardation for suppressing the occurrence of iridescence.
The upper limit of the thickness of the polarizer protective film 1 is preferably 80 μm, more preferably 75 μm, even more preferably 70 μm, and particularly preferably 65 μm. By setting the thickness below the above range, it becomes easier to make the display device thinner.

The lower limit of the ratio of the thickness of the polarizer protective film 1/the thickness of the polarizer protective film 4 (sometimes referred to simply as the thickness ratio) is preferably 0.5, more preferably 0.6, and still more preferably 0. 0.65, particularly preferably 0.7. The upper limit of the thickness ratio is preferably 0.97, more preferably 0.96, still more preferably 0.95. In addition, particularly preferred upper limits are 0.9, 0.85, or 0.8. By setting the thickness to be less than or equal to the above, the excess thickness is reduced, and it becomes easy to make the display device thinner.

In order to obtain the effects of the present invention while the polarizer protective films 1 and 4 have similar optical properties, it is also a preferred embodiment that the thickness ratio is more than 0.95 and 0.97 or less.

In the thickness ratio range, the warping of the liquid crystal panel is greatly affected by the contraction of the polarizer of the viewing side polarizing plate (in the long side direction of the screen; usually in the MD direction). Based on the knowledge that the strength of the polarizer protective film 4 of the light source side polarizing plate located on the side is important. In order to counteract the shrinkage of the polarizer of the viewer-side polarizing plate, for example, the strength against the shrinkage of the polarizer protective film 1 of the viewer-side polarizer in the MD direction of the polarizer and the polarization of the light source-side polarizer It is necessary to have strength to resist the extension of the protective film 4 in the TD direction. Since the strength in the TD direction is high, making the polarizer protective film 4 thicker than the polarizer protective film 1 may be advantageous for suppressing warpage of the liquid crystal panel. In other words, if the polarizer protective film 1 and the polarizer protective film 4 have the same thickness, the polarizer protective film 1 has an excessive thickness, which may be disadvantageous for further thinning.

The lower limit of the total film thickness of the polarizer protective film 1 and the polarizer protective film 4 is preferably 90 μm, more preferably 95 μm, still more preferably 100 μm. When the thickness is above the above, it becomes easy to suppress the warp of the liquid crystal panel, and it becomes easy to secure Re and suppress the occurrence of iridescence.
The upper limit of the total film thickness of the polarizer protective film 1 and the polarizer protective film 4 is preferably 155 μm, more preferably 150 μm, still more preferably 145 μm. By setting the thickness below the above range, it becomes easier to make the display device thinner.

The warp of the liquid crystal panel varies depending on the shrinkage force of the polarizer, the size of the liquid crystal display device, and the like. Therefore, the effect of the present invention does not necessarily mean that the thickness of the polarizer protective film is preferably not more than a specific value in all cases. This means that it becomes possible to make the device thinner.

In the examples, the thickness and retardation of the polarizer protective film are measured in the state of the base film, but after being processed as a polarizing plate, the polarizing plate is cut out and the cross section is examined with an optical microscope or an electron microscope. You may observe and measure thickness. Refractive index measurement for obtaining retardation is performed by peeling off the polarizer protective film, polishing or scraping off any adhesive layer or functional layer on the surface, and then measuring the refractive index of the base film. may
Further, these values can be the average values measured at 5 points in both the long side direction and the short side direction from positions about 5 cm from each end, totaling 5×5=25 points.

The resins used for the polarizer protective films 1 and 4 are not particularly limited as long as they cause birefringence due to orientation, but polyester, polycarbonate, polystyrene and the like are preferable independently from the viewpoint of increasing the retardation. Polyester is particularly preferred. Preferable polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polytetramethylene terephthalate (PBT), and polyethylene naphthalate (PEN), among which PET and PEN are preferred.

In the case of PET, the intrinsic viscosity (IV) of the resin constituting the film is preferably 0.5 to 1.5 dL/g. The lower limit of the intrinsic viscosity (IV) is more preferably 0.55 dL/g, still more preferably 0.58 L/g, particularly preferably 0.6 dL/g. The upper limit of the intrinsic viscosity (IV) is more preferably 1.2 dL/g, still more preferably 1 dL/g. When it is 0.5 dL/g or more, mechanical strength such as impact resistance is excellent, and the production of the film is easy. Manufacture of a film is easy as it is 1.5 dL/g or less. The intrinsic viscosity (IV) is measured by dissolving in a mixed solvent of phenol/1,1,2,2-tetrachloroethane (=3/2; weight ratio) at a temperature of 30°C.

The polarizer protective films 1 and 4 each independently desirably have a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance is more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of iodine and dichroic dye in the polarizing layer due to ultraviolet rays can be suppressed. The light transmittance at a wavelength of 380 nm is measured in the direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500).

The light transmittance at a wavelength of 380 nm of the base film contained in the polarizer protective films 1 and 4 is set to 20% or less by adding an ultraviolet absorber to the base film, and a coating liquid containing the ultraviolet absorber. can be achieved by applying to the surface of the substrate film, appropriately adjusting the type and concentration of the ultraviolet absorber, and the thickness of the substrate film. UV absorbers are known substances. Examples of the UV absorber include organic UV absorbers and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency.

Examples of the organic UV absorber include benzotriazole, benzophenone, cyclic iminoester, and combinations thereof, but are not particularly limited as long as the above light transmittance can be obtained.

It is also preferable to add particles having an average particle diameter of 0.05 to 2 μm to the base film in order to improve slipperiness. The particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride. , styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based organic polymer particles.
These particles may be added to the entire base film, or may be added only to the skin layer in a skin-core coextruded multilayer structure.

The polarizer protective films 1 and 4 can be obtained according to a general film manufacturing method. A case where the polarizer protective films 1 and 4 are polyester films such as PET films will be described as an example. Hereinafter, in the description of the manufacturing method, the polarizer protective films 1 and 4 may be referred to as polyester films. For example, as a method for producing a polyester film, a polyester resin is melted, a non-oriented polyester that is extruded into a sheet is stretched in the longitudinal direction and/or the transverse direction at a temperature equal to or higher than the glass transition temperature, and a heat treatment is performed. are mentioned.

The polyester film may be uniaxially stretched or biaxially stretched, but uniaxial stretching is preferred because a greater biaxiality requires a greater thickness in order to ensure the necessary retardation.

The main orientation axis of the polyester film may be the running direction of the film (longitudinal direction, MD direction) or a direction perpendicular to the longitudinal direction (width direction, TD direction). In the case of MD stretching, roll stretching is preferred, and in the case of TD stretching, tenter stretching is preferred.

In stretching, the polyester film is preheated and stretched at preferably 80 to 130°C, more preferably 90 to 120°C. The draw ratio is preferably 3 to 7 times, more preferably 3.5 to 6.5 times, still more preferably 3.8 to 6.2 times.
Moreover, in order to further enhance uniaxiality, it is also preferable to shrink the film in a direction orthogonal to the stretching direction during stretching. In the case of TD stretching in a tenter, shrinkage can be achieved, for example, by narrowing the tenter clip spacing. The shrinkage treatment is preferably 1 to 20%, more preferably 2 to 15%.

In the case of biaxial stretching, the above is the main stretching, and before the main stretching, it is stretched 1.1 to 2 times in a direction orthogonal to the main stretching, preferably 1.2 to 1.8 times. preferable.

Stretching is preferably followed by heat setting. The heat setting temperature is preferably 150 to 250°C, more preferably 170 to 230°C. In heat setting, it is also preferable to perform a relaxation treatment in the main stretching direction or in a direction orthogonal thereto. The relaxation treatment is preferably 0.5 to 10%, more preferably 1 to 5%.

The polyester film after heat setting is wound into a roll after cooling. Additional slight stretching in the main stretching direction during the cooling process is also preferable for reducing warping of the liquid crystal panel. The additional slight stretching is preferably carried out at a polyester film temperature of 80 to 150° C., and the magnification is preferably 1 to 5%, more preferably 1.5 to 3%.

The polarizer protective films 1 and 4 may be subjected to a treatment for improving adhesiveness such as corona treatment, flame treatment, plasma treatment, or the like.

The polarizer protective films 1 and 4 are provided with an easy-adhesion layer ( An easy adhesion layer P1) may be provided.
Polyester resins, polyurethane resins, polycarbonate resins, acrylic resins, and the like are used as resins used for the easy-adhesion layer, and polyester resins, polyester-polyurethane resins, polycarbonate-polyurethane resins, and acrylic resins are preferred. It is preferable that the resin used for the easy-adhesion layer is crosslinked. Examples of cross-linking agents include isocyanate compounds, melamine compounds, epoxy resins, oxazoline compounds, and the like. Addition of a water-soluble resin such as polyvinyl alcohol is also a useful means for improving adhesion to the polarizer.

The easy-adhesion layer can be provided by coating and drying the polarizer protective films 1 and 4 as a water-based paint containing these resins and, if necessary, a cross-linking agent, particles, and the like. Examples of particles include those added to the base film described above.
The easy-adhesion layer may be provided off-line on the stretched film, but is preferably provided in-line during the film-forming process. When provided in-line, it may be applied before longitudinal stretching or before transverse stretching, but it is applied before transverse stretching (especially immediately before transverse stretching), preheated by a tenter, heated, and dried and crosslinked in the heat treatment process. is preferred. In the case of in-line coating before longitudinal stretching by rolls (especially immediately before longitudinal stretching), it is preferable to dry with a vertical dryer after coating and then lead to stretching rolls.
The coating amount (coating amount after drying) of the easily adhesive layer is preferably 0.01 to 1.0 g/m ² , more preferably 0.03 to 0.5 g/m ² .

A hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, and an antistatic layer are independently provided on the sides of the polarizer protective films 1 and 4 opposite to the side on which the polarizer (or polarizing film) is laminated. It is also a preferred form that a functional layer such as a layer is provided. In particular, the polarizer protective film 1 is often the outermost surface (near the visible side surface) of the liquid crystal display device, and is provided with any one of an antireflection layer, a low reflection layer, and an antiglare layer. preferable. An antireflection layer, a low reflection layer, an antiglare layer, and the like are collectively referred to as a reflection reduction layer. The reflection-reducing layer not only prevents external light from being reflected on the liquid crystal display screen and makes it difficult to see, but also has the effect of suppressing reflection at the interface to reduce iridescence or make it less noticeable. In addition, in the polarizer protective films 1 and 4 provided with the functional layer, the film in the state before the functional layer is provided is referred to as a base film. In addition, the substrate film may contain the above-described easy-adhesion layer.

The upper limit of the reflectance of the polarizer protective film measured from the reflection reducing layer side is preferably 5%, more preferably 4%, even more preferably 3%, particularly preferably 2%, and most preferably. is 1.5%. If it is less than the above, it does not affect iridescence and color reproducibility.
Although the lower limit of the reflectance is not particularly limited, it is preferably 0.01%, and more preferably 0.1% from a practical point of view.

(low reflection layer)
The low-reflection layer is a layer having a function of reducing the reflectance by providing a low-refractive-index layer on the surface of the base film to reduce the difference in refractive index from air.

(Antireflection layer)
The antireflection layer controls the thickness of the low refractive index layer so that the upper interface of the low refractive index layer (e.g., low refractive index layer-air interface) and the lower interface of the low refractive index layer (e.g., substrate film - interface of the low refractive index layer) to control reflection by causing interference of reflected light. In this case, the thickness of the low refractive index layer is preferably about the wavelength of visible light (400 to 700 nm)/(refractive index of low refractive index layer×4).
It is also a preferable form to provide a high refractive index layer between the antireflection layer and the base film, and two or more low refractive index layers and high refractive index layers are provided to further enhance the antireflection effect by multiple interference. good too.

In the case of the antireflection layer, the upper limit of the reflectance is preferably 2%, more preferably 1.5%, even more preferably 1.2%, and particularly preferably 1%.

(Low refractive index layer)
The refractive index of the low refractive index layer is preferably 1.45 or less, more preferably 1.42 or less. Moreover, the refractive index of the low refractive index layer is preferably 1.2 or more, more preferably 1.25 or more.
The refractive index of the low refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the low-refractive-index layer is not limited, but it may be appropriately set within the range of about 30 nm to 1 μm. In addition, if the purpose is to further lower the reflectance by canceling the reflection on the surface of the low refractive index layer and the interface reflection between the low refractive index layer and its inner layer (base film, hard coat layer, etc.) The thickness of the low refractive index layer is preferably 70-120 nm, more preferably 75-110 nm.

The low refractive index layer preferably includes (1) a layer made of a resin composition containing a binder resin and low refractive index particles, (2) a layer made of a fluororesin that is a low refractive index resin, (3) silica or Examples include a layer made of a fluororesin composition containing magnesium fluoride, and (4) a thin film of a low refractive index substance such as silica and magnesium fluoride.

As the binder resin contained in the resin composition (1), polyester, polyurethane, polyamide, polycarbonate, acryl, etc. can be used without particular limitation. Among them, acrylic is preferred, and one obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation is preferred.

Photopolymerizable compounds include photopolymerizable monomers, photopolymerizable oligomers, and photopolymerizable polymers, and these can be appropriately adjusted and used. The photopolymerizable compound is preferably a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer. These photopolymerizable monomers, photopolymerizable oligomers and photopolymerizable polymers are preferably polyfunctional.

Examples of polyfunctional monomers include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), and dipentaerythritol pentaacrylate (DPPA). In addition, a monofunctional monomer may be used in combination for adjustment of coating viscosity and hardness.

Polyfunctional oligomers include polyester (meth)acrylate, urethane (meth)acrylate, polyester-urethane (meth)acrylate, polyether (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, and isocyanurate (meth)acrylate. Acrylate, epoxy (meth)acrylate and the like.

Polyfunctional polymers include urethane (meth)acrylate, isocyanurate (meth)acrylate, polyester-urethane (meth)acrylate, epoxy (meth)acrylate and the like.

In addition to the above components, the resin composition (1) may contain a polymerization initiator, a cross-linking agent catalyst, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a leveling agent, a surfactant, and the like. .

Examples of the low refractive index particles contained in the resin composition (1) include silica particles (for example, hollow silica particles), magnesium fluoride particles, etc. Among them, hollow silica particles are preferred. Such hollow silica particles can be produced, for example, by the production method described in Examples of JP-A-2005-099778.

The average particle size of the primary particles of the low refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, even more preferably 10 to 80 nm.

The low refractive index particles are more preferably surface-treated with a silane coupling agent, and more preferably surface-treated with a silane coupling agent having a (meth)acryloyl group.

The content of the low refractive index particles in the low refractive index layer is preferably 10 to 250 parts by mass, more preferably 50 to 200 parts by mass, and even more preferably 100 to 180 parts by mass with respect to 100 parts by mass of the binder resin.

As the fluororesin (2), a polymerizable compound containing at least a fluorine atom in the molecule or a polymer thereof can be used. The polymerizable compound is not particularly limited, but preferably has a curing reactive group such as a photopolymerizable functional group or a thermosetting polar group. A compound having these multiple curing reactive groups at the same time may also be used. In contrast to this polymerizable compound, the polymer does not have the above curing reactive groups.

As a compound having a photopolymerizable functional group, for example, a fluorine-containing monomer having an ethylenically unsaturated bond can be widely used.

For the purpose of improving anti-fingerprint properties, it is also preferable to appropriately add a known polysiloxane-based or fluorine-based antifouling agent to the low refractive index layer.

The surface of the low-refractive-index layer may be an uneven surface in order to provide antiglare properties, but it is also preferable that it is a smooth surface.
When the surface of the low refractive index layer is a smooth surface, the arithmetic mean roughness Ra (JIS B0601:1994) of the surface of the low refractive index layer is preferably 20 nm or less, more preferably 15 nm or less, and still more preferably. is 10 nm or less, particularly preferably 8 nm or less, and usually 1 nm or more. The ten-point average roughness Rz (JIS B0601:1994) of the surface of the low refractive index layer is preferably 160 nm or less, more preferably 155 nm or less, and usually 50 nm or more.

The refractive index of the high refractive index layer is preferably 1.55 or more, more preferably 1.56 or more. The refractive index of the high refractive index layer is preferably 1.85 or less, more preferably 1.8 or less, even more preferably 1.75 or less, and even more preferably 1.7 or less.
The refractive index of the high refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the high refractive index layer is preferably 30 to 200 nm, more preferably 50 to 180 nm. Although the high refractive index layer may be a plurality of layers, it is preferably two layers or less, more preferably a single layer. In the case of multiple layers, the total thickness of the multiple layers is preferably within the above range.

When two high refractive index layers are used, the refractive index of the high refractive index layer on the low refractive index layer side is preferably higher. Specifically, the refractive index of the high refractive index layer on the low refractive index layer side is The index is preferably 1.6 to 1.85, and the refractive index of the other high refractive index layer is preferably 1.55 to 1.7.

The high refractive index layer is preferably made of a resin composition containing high refractive index particles and a resin.
Among them, antimony pentoxide particles, zinc oxide particles, titanium oxide particles, cerium oxide particles, tin-doped indium oxide particles, antimony-doped tin oxide particles, yttrium oxide particles, and zirconium oxide particles are preferable as the high refractive index particles. Among these, titanium oxide particles and zirconium oxide particles are preferred.

Two or more kinds of high refractive index particles may be used in combination. In particular, it is also preferable to add the first high refractive index particles and the second high refractive index particles having a smaller surface charge amount to prevent aggregation. It is also preferable from the standpoint of dispersibility that the high refractive index particles are surface-treated.

The preferred average particle size of the primary particles of the high refractive index particles is the same as that of the low refractive index particles.

The content of the high refractive index particles is preferably 30 to 400 parts by mass, more preferably 50 to 200 parts by mass, and further preferably 80 to 150 parts by mass with respect to 100 parts by mass of the resin. preferable.

The resins used for the high refractive index layer are the same as those mentioned for the low refractive index layer except for the fluororesin.

In order to flatten the low refractive index layer provided on the high refractive index layer, it is preferable that the surface of the high refractive index layer is also flat.

The high-refractive-index layer and the low-refractive-index layer are formed, for example, by applying a coating material containing the above photopolymerizable compound to a substrate film, drying the coating material, and irradiating the coating material with light such as ultraviolet rays. , can be formed by polymerizing (crosslinking) a photopolymerizable compound.

If necessary, a thermoplastic resin, a thermosetting resin, a solvent, and a polymerization initiator may be added to the paint for forming the high refractive index layer and the low refractive index layer. In addition, dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, anti-coloring agents, coloring agents (pigments, dyes), antifoaming agents, leveling agents, flame retardants, UV absorbers, adhesion imparting agents agents, polymerization inhibitors, antioxidants, surface modifiers, lubricants and the like may be added.

(Antiglare layer)
The anti-glare layer is a layer that prevents reflection of the shape of a light source when external light is reflected on the surface and reduces glare, by providing irregularities on the surface to cause diffuse reflection.

The arithmetic mean roughness (Ra) of unevenness on the surface of the antiglare layer is preferably 0.25 μm or less, more preferably 0.2 μm or less, still more preferably 0.15 μm or less, and even more preferably It is 0.12 μm or less, and usually 0.02 μm or more.

The ten-point average roughness (Rzjis) of unevenness on the surface of the antiglare layer is preferably 0.15 μm or more, more preferably 0.2 μm or more, still more preferably 0.25 μm or more, and even more preferably. is 0.3 μm or more. Rzjis is preferably 2 μm or less, more preferably 1.5 μm or less, still more preferably 1.2 μm or less, even more preferably 1 μm or less, and particularly preferably 0.8 μm or less. .

Ra and Rzjis are calculated from a roughness curve measured using a contact roughness meter in accordance with JIS B0601-1994 or JIS B0601-2001.

Examples of methods for providing the antiglare layer on the base film include the following methods.
・Apply anti-glare layer paint containing particles (filler), etc. ・Cure the anti-glare layer resin while it is in contact with the mold with uneven structure. Apply to the mold and transfer to the base film ・Apply a paint that causes spinodal decomposition during drying and film formation

The lower limit of the thickness of the antiglare layer is preferably 0.1 μm, more preferably 0.5 μm. The upper limit of the thickness of the antiglare layer is preferably 100 µm, more preferably 50 µm, and still more preferably 20 µm.

The refractive index of the antiglare layer is preferably 1.2 or higher, more preferably 1.3 or higher, and still more preferably 1.4 or higher. Moreover, the refractive index of the antiglare layer is preferably 1.8 or less, more preferably 1.7 or less.
When the refractive index of the antiglare layer itself is lowered to obtain a low reflection effect, the refractive index of the antiglare layer is preferably 1.2 to 1.45, more preferably 1.25 to 1.4.
When the low refractive index layer described below is provided on the antiglare layer, the refractive index of the antiglare layer is preferably 1.5 to 1.8, more preferably 1.55 to 1.7.
The refractive index of the antiglare layer is a value measured under the condition of a wavelength of 589 nm.

The low refractive index layer may be provided with unevenness to serve as an antiglare and low reflection layer, or an antiglare and antireflection layer may be provided by providing a low refractive index layer on the unevenness of the antiglare layer to provide an antireflection function.

(Hard coat layer)
It is also a preferred form to provide a hard coat layer as a lower layer of the reflection reducing layer.
The hard coat layer preferably has a pencil hardness of H or more, more preferably 2H or more. The hard coat layer is made of, for example, a resin composition containing a cured product of a thermosetting resin or a radiation-curable resin, and can be provided by applying and curing a coating material for forming a hard coat layer.

Thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea melamine resins, epoxy resins, unsaturated polyester resins, silicone resins, combinations thereof, and the like. The thermosetting resin coating for forming a hard coat layer contains, if necessary, a curing agent, a catalyst, and a coating for forming the high refractive index layer and the low refractive index layer. Additives and the like may be added.

The radiation-curable resin is preferably a compound having a radiation-curable functional group. Examples of the radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, and epoxy groups. , oxetanyl group, and the like. Among these, as the ionizing radiation-curable compound, a compound having an ethylenically unsaturated bond group is preferable, and a compound having two or more ethylenically unsaturated bond groups is more preferable. Polyfunctional (meth)acrylate compounds having the above are more preferable. A polyfunctional (meth)acrylate compound may be a monomer, an oligomer, or a polymer.

As specific examples thereof, those mentioned as the binder resin are used.
In order to achieve hardness as a hard coat, the difunctional or higher monomer content in the compound having a radiation-curable functional group is preferably 50% by mass or more, more preferably 70% by mass or more. Furthermore, in the compound having a radiation-curable functional group, the trifunctional or higher monomer preferably accounts for 50% by mass or more, more preferably 70% by mass or more.
The compounds having a radiation-curable functional group can be used singly or in combination of two or more. If necessary, a catalyst, additives contained in the paint for forming the high refractive index layer and the low refractive index layer, and the like are added to the coating material for forming the hard coat layer of the radiation-curable resin.

The thickness of the hard coat layer is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, even more preferably in the range of 0.8 to 20 μm.

The refractive index of the hard coat layer is preferably 1.45 or higher, more preferably 1.5 or higher. Moreover, the refractive index of the hard coat layer is preferably 1.7 or less, more preferably 1.6 or less.
The refractive index of the hard coat layer is a value measured at a wavelength of 589 nm.

Examples of adjusting the refractive index of the hard coat layer include a method of adjusting the refractive index of the resin, and a method of adjusting the refractive index of the particles when particles are added.
Examples of the particles include those exemplified as the particles of the antiglare layer.
In the present invention, the hard coat layer is sometimes referred to as a reflection reducing layer.

When providing a functional layer, you may provide an easy-adhesion layer (easy-adhesion layer P2) between a functional layer and a base film. For the easy-adhesion layer P2, the resins, cross-linking agents, and the like mentioned for the easy-adhesion layer P1 are preferably used. Also, the easy-adhesion layer P1 and the easy-adhesion layer P2 may have the same composition or different compositions.
It is preferable that the easily bonding layer P2 is also provided in-line. The easy-adhesion layer P1 and the easy-adhesion layer P2 may be sequentially coated and dried, but simultaneous coating on both sides is also a preferred form.

As a polarizer used in the polarizing plate, for example, uniaxially stretched polyvinyl alcohol (PVA) to which iodine or an organic dichroic dye is adsorbed, or a liquid crystal compound and an organic dichroic dye to be oriented. Alternatively, a liquid crystalline polarizer containing a liquid crystalline dichroic dye, a wire grid type polarizer, or the like can be used without particular limitation.

A film-shaped polarizer made by adsorbing iodine or an organic dichroic dye to uniaxially stretched polyvinyl alcohol (PVA) and a base film wound in a roll are bonded using PVA-based, UV-curing, etc. It can be laminated using an adhesive or adhesive and wound into a roll. The thickness of this type of polarizer is preferably 5 to 50 μm, more preferably 10 to 30 μm, particularly preferably 12 to 25 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

There is also a polarizer in which PVA is applied to an unstretched release film (substrate) such as a PET film or polypropylene film, and uniaxially stretched together with the release film to adsorb iodine or an organic dichroic dye. It is preferably used. In the case of this polarizer, the polarizer surface of the polarizer laminated on the release film (the surface on which the release film is not laminated) and the base film are laminated with an adhesive or adhesive, and then the polarizer is attached. The base film and the polarizer can be bonded together by peeling off the release film used in the production. Also in this case, it is preferable to stick together in a roll form and take up the roll. The thickness of this type of polarizer is preferably 1 to 10 μm, more preferably 2 to 8 μm, particularly preferably 3 to 6 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

In the case of a liquid crystalline polarizer, a polarizer composed of a liquid crystal compound and an organic dichroic dye is laminated on a base film, or a liquid crystalline dichroic dye is laminated on the base film. A polarizing plate can be obtained by applying a coating liquid containing the above, drying it, and photo- or heat-curing it to laminate a polarizer. Examples of the method for orienting the liquid crystalline polarizer include a method of rubbing the surface of the object to be coated and a method of irradiating polarized ultraviolet rays to cure the liquid crystalline polarizer while aligning it. The surface of the substrate film may be rubbed directly and then coated with the coating liquid, or the substrate film may be directly coated with the coating liquid and irradiated with polarized ultraviolet rays. It is also a preferable method to provide an orientation layer on the base film before providing the liquid crystalline polarizer (that is, to laminate the liquid crystalline polarizer on the base film via the orientation layer). As a method for providing the orientation layer,
- A method of coating polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resin, polysiloxane derivative, etc., and rubbing the surface thereof to form an alignment layer (rubbing alignment layer);
- A method of applying a coating solution containing a polymer or monomer having a photoreactive group such as a cinnamoyl group or a chalcone group and a solvent, and irradiating polarized ultraviolet rays to harden the alignment layer (photoalignment layer), etc. are mentioned.

A liquid crystalline polarizer is provided on the release film according to the above method, the liquid crystalline polarizer surface and the base film are laminated with an adhesive or a pressure-sensitive adhesive, and then the release film is peeled off to remove the base film. A material film and a polarizer can also be pasted together.

The thickness of the liquid crystalline polarizer is preferably 0.1 to 7 μm, more preferably 0.3 to 5 μm, particularly preferably 0.5 to 3 μm. The thickness of the adhesive or adhesive is preferably 1-10 μm, more preferably 2-5 μm.

Although the angle formed by the absorption axis of the polarizer and the slow axis of the polarizer protective film 1 or 4 is not particularly limited, it is preferably parallel or orthogonal. "Parallel or orthogonal" allows a deviation from 0 degree or 90 degrees, preferably ±10 degrees, more preferably ±7 degrees, and particularly preferably ±5 degrees. By making them parallel or orthogonal, it is possible to easily stick them together in a roll form and wind them up. In particular, in the case of a polarizer obtained by adsorbing iodine or an organic dichroic dye to uniaxially stretched polyvinyl alcohol (PVA), it is generally stretched in the MD direction, and the polarizer protective film 1 and 4 is often stretched in the TD direction. Therefore, when both are bonded together in a roll form, the absorption axis of the polarizer and the slow axis of the polarizer protective film are often perpendicular to each other.

The surface of the polarizer on the liquid crystal cell side may be directly attached to the liquid crystal cell with an adhesive or adhesive, or a cured layer may be provided on the surface of the polarizer on the liquid crystal cell side. or 3 may be provided. Examples of the cured layer include the hard coat layer described above.

The polarizer protective films 2 and 3 may each independently be a cellulose-based (TAC) film, an acrylic film, a polycyclic olefin (COP) film, or the like. At least one of the polarizer protective films 2 and 3 may have substantially zero retardation, and is a retardation film (optical compensation film) for controlling changes in color tone when the display screen is viewed from an oblique direction. may be

In order to obtain the necessary retardation in the optical compensation film, the film should be stretched, or a retardation layer such as a liquid crystal compound should be applied on the film. A method such as providing and transferring this is exemplified. A liquid crystal compound for forming the retardation layer may be a rod-like liquid crystal compound, a discotic liquid crystal compound, or the like, depending on the required retardation characteristics. The liquid crystal compound preferably has a photocurable reactive group such as a double bond in order to fix the alignment state. In order to align the liquid crystal compound and provide a retardation, an alignment layer is provided as a lower layer of the retardation layer, and the alignment layer is rubbed or irradiated with polarized ultraviolet rays to coat on the alignment layer. Alignment controllability such that the liquid crystal compound is aligned in a specific direction can be imparted.

The retardation of the optical compensation film can be appropriately set depending on the type of liquid crystal cell to be used, the viewing angle to be secured, and the like.

The retardation layer can be provided by applying a composition paint for retardation layer. The composition paint for retardation layer may contain a solvent, a polymerization initiator, a sensitizer, a polymerization inhibitor, a leveling agent, a polymerizable non-liquid crystal compound, a cross-linking agent and the like. As these materials, the materials described in the alignment layer and the liquid crystal polarizer can be used.

A retardation layer can be provided by coating the composition paint for retardation layer on the release surface of the release film or the orientation layer (orientation control layer), followed by drying, heating and curing.

As for these conditions, the conditions explained in the sections of the alignment layer and the liquid crystal polarizer are used as preferable conditions.

When bonding the polarizer and the polarizer protective film together, an adhesive or pressure-sensitive adhesive is used. As the adhesive, a water-based adhesive such as a polyvinyl alcohol-based adhesive or a photocurable adhesive is preferably used. An acrylic adhesive is preferably used as the adhesive.

A liquid crystal cell is preferably one in which a liquid crystal compound is sealed between thin substrates such as glass on which a circuit is formed. When the substrate is glass, the thickness is preferably 0.7 mm or less, more preferably 0.5 mm or less, and still more preferably 0.4 mm or less from the viewpoint of thinning.

The method of the liquid crystal cell is not particularly limited, but in the VA method and the IPS method, the absorption axis of the polarizing plate on the viewing side is provided so as to be parallel or perpendicular to the long side direction of the liquid crystal cell. is the preferred method for applying

A liquid crystal panel can be formed by attaching polarizing plates to the viewing side and the light source side of the liquid crystal cell. It is preferable that the bonding is performed with an acrylic pressure-sensitive adhesive.

As backlight sources for liquid crystal display devices, RGB three-color LEDs, a combination of blue LEDs and yellow phosphors, a combination of blue LEDs and green/red phosphors, and a combination of UV LEDs and blue/green phosphors can be used. Combinations of phosphors and red phosphors, organic EL light emitters, and the like can be used without limitation. In particular, a blue LED light source that is wavelength-converted into green or red by quantum dot particles, generally called a QD light source, and a KSF light source that uses a fluoride phosphor such as K ₂ SiF ₆ :Mn ⁴⁺ as a red phosphor, is generally a KSF light source. is a light source that is preferably used because of its wide color gamut.

The backlight source is preferably used as a light source unit in which a reflector, a light guide plate, a diffusion plate, a lens sheet, and a prism sheet are laminated as necessary in a liquid crystal display device. A reflective polarizing plate called a brightness enhancement film may be installed on the viewing side of the light source unit.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate modifications within the scope of the gist of the present invention. Both of them are included in the technical scope of the present invention.

Methods for evaluating physical properties in Examples are as follows.
(1) Refractive index of polyester film
Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the slow axis direction of the film was determined, and the slow axis direction was parallel to the long side. A rectangle was cut out and used as a sample for measurement. For this sample, the refractive index in the orthogonal biaxial direction (refractive index in the slow axis direction: ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): nx), and the refractive index in the thickness direction (nz ) was determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm).

(2) In-plane retardation (Re)
The in-plane retardation is defined as the product (ΔNxy×d) of the anisotropy of the biaxial refractive index (ΔNxy=|nx−ny|) and the film thickness d (nm) on the film. It is a parameter and a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) is determined by the method (1) above, and the absolute value of the biaxial refractive index difference (|nx−ny|) is calculated as the refractive index anisotropy (Δ Nxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co.) and converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(3) Thickness direction retardation (Rth)
The retardation in the thickness direction is obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) when viewed from the cross section in the thickness direction of the film by the film thickness d. It is a parameter that indicates the average retardation. Obtain nx, ny, nz and film thickness d (nm) in the same manner as for measuring retardation, and calculate the average value of (ΔNxz × d) and (ΔNyz × d) to obtain thickness direction retardation (Rth). asked for

(4) NZ coefficient Obtain nx, ny, and nz in the same manner as for retardation measurement, and substitute nx, ny, and nz into the formula represented by |ny-nz|/|ny-nx| to obtain Nz I found the coefficient.

After the film was formed, the refractive index and the thickness were measured at two points about 5 cm inside from both ends in the TD direction for each polarizer protective film slit for bonding with the polarizer, and 3 points at equal intervals therebetween. The same procedure was performed at 5 points with an interval of about 20 cm in the MD direction, and the average of a total of 25 points (5×5=25) was obtained. Note that the notation in the table is the value rounded off to the first decimal place.

(5) Warp of panel A simulated cell was formed by bonding polarizing plates to both sides of a 0.5 mm-thick, 43-inch glass plate in a crossed Nicols manner in the same manner as in the examples and comparative examples. For bonding, an optical substrate-less pressure-sensitive adhesive sheet was used.
The prepared simulated cell was heat-treated for 240 hours in a gear oven set to 70 ° C. and 5% RH, and then cooled for 30 minutes in an environment set to room temperature 25 ° C. and 50% RH. Placed on a horizontal surface with the side facing down, the height of the four corners was measured with a measure, and the maximum value was taken as the amount of warpage. The amount of warpage was evaluated as follows. In addition, the simulated cell is supported by prisms at the four corners, and the above heat treatment and cooling are performed in a state in which the panel is placed horizontally on the prisms (that is, the simulated cell is floating except for the four corners). processed.
○: 0 mm or more and less than 2 mm △: 2 mm or more and less than 4 mm ×: 4 mm or more

(6) Acceptable angle of rainbow spots A backlight unit and a liquid crystal panel were taken out from a commercially available television (REGZA 43J10X manufactured by Toshiba Corporation), and the polarizing plate of the liquid crystal panel was peeled off. The polarizing plate using the polarizer protective films A to K prepared on the liquid crystal panel surface from which the polarizing plate was peeled is placed so that the polarizer protective films A to K are on the opposite side of the liquid crystal cell with the polarizer sandwiched therebetween. After arranging the polarizer so that the absorption axis direction of the polarizer is the same as that of the original polarizing plate, a backlight unit was attached to obtain a display for evaluation. The space between the liquid crystal cell and the polarizing plate was filled with deionized water to prevent reflection. The display for evaluation was placed horizontally on a desk and displayed entirely in white, and the state of the iridescent spot in the central portion of the display was observed while moving from the normal direction to the determined azimuth angle direction. The angle (polar angle) between the normal direction of the display and the straight line connecting the center of the display at the position where the rainbow spot started to appear and the center of both eyes of the observer was measured. The same was done with 5 observers and the mean value was taken as the acceptance angle of the iris.
(6-1) Allowable angle (degrees) of rainbow spot on light source side
Only the light source side polarizing plate was replaced, and the azimuth angle was set to 30 degrees with the transmission axis direction of the polarizer used for the light source side polarizing plate (main orientation axis direction of the polarizer protective film).
(6-2) Permissible angle (degrees) of rainbow spot on viewing side
Only the viewer-side polarizing plate was replaced, and the azimuth angle was adjusted to 30 degrees with the transmission axis direction of the polarizer used for the viewer-side polarizing plate (main orientation axis direction of the polarizer protective film).
(6-3) Acceptable angle (degrees) of rainbow spot of display with exchanged polarizers on both sides
The polarizing plates on both sides are exchanged, and the azimuth angle is set to 30 degrees, 45 degrees, or 60 degrees from the transmission axis direction of the polarizer used for the viewing side polarizing plate (the main orientation axis direction of the polarizer protective film), and the maximum allowable angle is Acceptance angle at narrow azimuth was adopted.

Polyester A (PET (A))
Polyethylene terephthalate polyester B (PET (B)) with an intrinsic viscosity of 0.62 dl/g
A molten mixture of 10 parts by mass of an ultraviolet absorber (2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one) and 90 parts by mass of PET (A).

(Preparation of adhesion-improving coating liquid)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method to obtain 46 mol % of terephthalic acid, 46 mol % of isophthalic acid, and 8 mol % of sodium 5-sulfonatoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components). , a water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol % of ethylene glycol and 50 mol % of neopentyl glycol (based on the total glycol component) as glycol components was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant are mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal group-containing copolymerized polyester resin and continuing to stir until the lumps of the resin disappear, the resin aqueous dispersion was cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A homogeneous water-dispersible copolyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silysia 310) in 50 parts by mass of water, Silysia 310 was added to 99.46 parts by mass of the water-dispersible copolymer polyester resin liquid. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added while stirring to obtain an adhesion-improving coating liquid.

(Polarizer)
A roll-shaped polyvinyl alcohol film with a thickness of 80 μm that was continuously dyed in an aqueous iodine solution was stretched 5 times in the transport direction and dried to obtain a long polarizer.

(Polarizer protective film A)
After drying under reduced pressure (1 Torr) at 135° C. for 6 hours, 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber as raw materials for the base film intermediate layer. , supplied to extruder 2 (for intermediate layer II layer), and PET (A) was dried by a conventional method, supplied to extruder 1 (for outer layer I layer and outer layer III), and melted at 285 ° C. . These two types of polymers are each filtered with a stainless sintered filter material (nominal filtration accuracy: 10 μm, 95% cut of particles), laminated in a two-type, three-layer confluence block, extruded in a sheet form from a nozzle, An unstretched film was produced by winding the film around a casting drum having a surface temperature of 30° C. and solidifying it by cooling using an electrostatic casting method. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, the adhesion-improving coating solution was applied to both surfaces of the unstretched PET film so that the coating amount after drying was 0.08 g/m ² , and dried at 80° C. for 20 seconds.

The unstretched film having the coating layer formed thereon was guided to a tenter stretching machine, and while gripping the ends of the film with a clip, was guided to a tenter at 100° C. and stretched 4 times in the width direction. Next, while maintaining the stretched width in the width direction, it is treated in a heat setting zone at a temperature of 190 ° C. for 10 seconds, and further subjected to a relaxation treatment of 2% in the width direction to obtain a uniaxially stretched PET film with a film thickness of 80 μm. rice field.

(Polarizer protective film B)
A polarizer protective film B was obtained in the same manner as the polarizer protective film A except that the thickness was changed.

(Polarizer protective film C)
A polarizer protective film C was obtained in the same manner as the polarizer protective film A except that the draw ratio was 5 times, the tenter temperature was 120° C., and the thickness of the film was changed.

(Polarizer protective film D, E, F)
Polarizer protective films D, E, and F were obtained in the same manner as polarizer protective film A, except that the draw ratio was 5 times, the tenter temperature was 110° C., and the film thicknesses were changed.

(Polarizer protective film G, H, I, J)
Polarizer protective films G, H, I, and J were obtained in the same manner as polarizer protective film A, except that the draw ratio was 5.6 times, the tenter temperature was 110° C., and the film thicknesses were changed.

Table 1 shows the properties of each polarizer protective film.

(Preparation of polarizing plate)
The polarizer protective film prepared above was laminated on one side of the polarizer, and the triacetyl cellulose film (thickness: 40 μm) was laminated on the opposite side by roll-to-roll. An ultraviolet curable adhesive was used for bonding. The polarizing plate was cut to the required size before being attached to the liquid crystal panel.

Examples 1-9, Comparative Examples 1-3
Panels were prepared according to the combination in Table 2 to measure the acceptance angle of the iridescence. Also, warpage of the panel was observed in a similar combination. Table 2 shows the results.

In Examples 1 to 9, the warp of the panel is within the permissible range, and the permissible angle of the iridescence is the same as the permissible angle when used alone on the light source side and the viewing side, and thinner thickness can be achieved. .
On the other hand, in Comparative Example 1, the same polarizer protective film polarizing plate was used on both the light source side and the viewing side. It can be seen that the allowable angle of spots is 59 degrees, the thickness of the polarizer protective film on the viewing side is excessive, and even though it is possible to further reduce the thickness, the thickness has not been reduced.
It can be seen that in Comparative Example 2, the thickness and retardation of the polarizer protective film of the light source side polarizing plate are excessive.
In Comparative Example 3, the polarizer protective film of the light source side polarizing plate was made too thin, so that it could not resist the contraction of the polarizer of the viewing side polarizing plate, resulting in conspicuous warping of the panel. In addition, the thickness of the polarizer protective film of the viewing side polarizing plate also has an excess.

According to the present invention, for example, it is possible to provide a thinner liquid crystal display device while preventing iridescence and warping of the liquid crystal panel.

Claims (6)

In a liquid crystal display device comprising a backlight source, a light source side polarizing plate, a liquid crystal cell, and a viewing side polarizing plate in this order, each of the light source side polarizing plate and the viewing side polarizing plate has at least one polarizer protective film and a polarizer. The polarizer protective film of the viewing side polarizing plate and located on the opposite side of the liquid crystal cell of the polarizer is the polarizer protective film 1, and the light source side polarizing plate is the polarizer protective film. When the polarizer protective film located on the opposite side of the polarizer to the liquid crystal cell is the polarizer protective film 4, the in-plane retardation of the polarizer protective film 4 is 5000 to 10000 nm, and the polarizer protective film 1 The ratio of the in-plane retardation of the polarizer protective film 4 to the in-plane retardation of the polarizer protective film 4 is 0.55 to 0.97. 2. The liquid crystal display device according to claim 1, wherein the polarizer protective film 1 has an in-plane retardation of 4500 to 9500 nm. 3. The liquid crystal display device according to claim 1, wherein the ratio of the in-plane retardation of the polarizer protective film 1/the in-plane retardation of the polarizer protective film 4 is 0.55 to 0.95. 4. Any one of claims 1 to 3, wherein the thickness of the polarizer protective film 4 is 50 to 95 μm, and the ratio of the thickness of the polarizer protective film 1/the thickness of the polarizer protective film 4 is 0.5 to 0.97. The liquid crystal display device described. 5. The liquid crystal display device according to claim 1, wherein the polarizer protective film 1 has a thickness of 40 to 80 μm. 6. The liquid crystal display device according to claim 1, wherein the ratio of the thickness of the polarizer protective film 1/the thickness of the polarizer protective film 4 is 0.5 to 0.95.