WO2009154011A1 - Liquid crystal display device - Google Patents

Abstract

Provided is a liquid crystal display device having therein a polarization plate capable of suppressing degrading of display by qualities avoiding occurrence of light leakage even when a screen is large. The liquid crystal display device comprises a front polarization plate, a liquid crystal panel, and a rear polarization plate in this order from the side of a display surface. At least the front polarization plate on the rear polarization plate has a laminated structure comprising a first polarizer and a second polarizer. The first polarizer consists of one polarizer and includes more areas of a low polarization degree than those the second polarizer includes. The second polarizer consists of a plurality of polarizers arranged side by side on the same surface.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device having a large display screen.

A liquid crystal display device is a display device that can be driven with low power consumption, and can be easily reduced in weight and thickness. Therefore, the liquid crystal display device is widely used in monitors for televisions, personal computers, monitors for portable terminals, and the like. A general liquid crystal display device usually has a pair of substrates, a liquid crystal display panel having a liquid crystal layer sandwiched between the pair of substrates, a pair of polarizing plates disposed on both sides of the liquid crystal display panel, and display light The light source etc. which irradiate the light used as are provided.

The polarizing plate has a polarizer that can convert natural light emitted from a light source into polarized light that vibrates in a certain direction. As a material of the polarizer, a material obtained by adsorbing an iodine complex or a dichroic dye on a polyvinyl alcohol (PVA: Poly フ ィ ル ム Alcohol) film is often used, and the polarizer is produced by stretching such a film. Is done. However, since a PVA-based film uses a hydrophilic polymer, it is very easy to be deformed and contracted particularly under humidified conditions, and the mechanical strength of the film itself is weak. Alternatively, a substrate such as TAC (Tri Acetyl Cellulose) that functions as a protective layer for protecting the polarizer is bonded to one surface. As a result, the strength of the polarizing plate is supplemented and the reliability of the polarizer is ensured.

In recent years, many liquid crystal display devices having a large screen size exceeding 60 inch type have been developed. For this reason, it is required to increase the area of a substrate such as glass as a base of the panel, and also a polarizing plate. However, it is currently difficult to manufacture a polarizing plate that can be used for a large-screen-size liquid crystal display device. This is because a method of making a polarizer having a required polarization characteristic a size applicable to a large screen size has not been established in terms of polarizing plate manufacturing technology.

Here, as a device for producing a larger polarizer, for example, when producing an alignment film of a liquid crystal panel using a photo-alignment method, a wire grid polarizing element for producing polarized light used for photo-alignment is used. And an arrangement method in which the light sources are arranged along the longitudinal direction of the light source (for example, see Patent Document 1). In this polarizer, a light shielding portion is disposed between the polarizers so that non-polarized light does not leak from the abutting portion of the polarizer.

On the other hand, as a device for dealing with the increase in size of an image display device that performs liquid crystal display, there is a method in which a plurality of liquid crystal display devices are arranged side by side and their end faces are abutted (for example, see Patent Document 2). ). In this image display device, the optical film is processed so that the end surfaces are not perpendicular to each other so that light leakage does not occur at the butted end surfaces of the plurality of liquid crystal display devices.
JP 2006-126464 A JP 2006-163377 A

As described above, in order to dispose a polarizing plate on a large-screen liquid crystal display device, it is necessary to jointly dispose a plurality of polarizing plates as a premise. However, there is room for improvement in that light leaks and becomes a factor of degrading display quality. In addition, there is room for further improvement in the technique of the above document in that the configuration becomes complicated.

The present invention has been made in view of the above-described present situation, and provides a liquid crystal display device in which a polarizing plate is arranged that does not cause light leakage even on a large screen and can suppress deterioration in display quality. It is intended to do.

In examining the polarizing plate applicable to a large screen, the present inventor first verified what display quality can be obtained with a liquid crystal display device in which polarizers are arranged side by side with respect to one display screen. Went. A plurality of polarizers arranged side by side with respect to one large substrate serving as a base inevitably have a gap of about several μm between the joined polarizers due to the bonding accuracy, It has been found that there is no polarizer in the gap area, and light leaks from the gap regardless of whether the display is on or off, and a bright line indicating a joint is visible on the display screen. In addition, the present inventor results in the expansion and contraction of the film constituting the polarizer due to high-temperature treatment such as high-temperature aging, or the use of the liquid crystal display device for a long period of time when manufacturing the liquid crystal display device. It has been found that the gap between the polarizers that become the joints is further widened, and a wider line is visually recognized on the display screen than when the polarizers were arranged.

Next, this inventor examined the method of extending the film used as a polarizer to the large screen size. If the polarization characteristics of the polarizer are not sufficient to obtain a sufficient degree of polarization (for example, to obtain a degree of polarization of 99.95% or more uniformly), a polarizer having a certain degree of polarization can be made into a large screen size. I found that I could stretch it. Some of the polarizers thus produced had a degree of polarization of 99.95% or more, and others had a degree of polarization of about 99.90%. When this was applied to a large-screen liquid crystal display device as it was, a liquid crystal display device with uneven display was obtained although a certain level of display quality was obtained.

Subsequently, the present inventor conducted various studies on means for solving each of the problems of these polarizers. As a result, a single polarizer with uneven polarization degree and a plurality of sheets arranged side by side with no uneven polarization degree. It was found that by arranging the polarizers arranged in the stack in an overlapping manner, each problem can be compensated and a good display can be obtained. The focus is on the property that, as long as the light finally passes through a region with sufficient polarization characteristics, it will be converted to polarized light as a result even if sufficient conversion to polarized light has not been performed before that. The polarized light may be either converted with a non-uniform polarizer or converted with a non-uniform polarizer, and by arranging in this way, The light transmitted through each polarizer is emitted as almost complete polarized light.

More specifically, when both polarizers are superposed as described above, if light is transmitted through a polarizing plate with unevenness, the light transmitted through a region having a sufficient degree of polarization is almost complete. On the other hand, even if the light is transmitted through a region that does not have a sufficient degree of polarization, it is then transmitted through the other non-uniform polarizer so that it is finally almost completely polarized. Will be emitted. Conversely, when light passes through a polarizer having a gap between the polarizers first, the light passing through the gap is not converted into polarized light, but it is sufficiently transmitted by passing through the other polarizer. As a whole, almost all light is finally converted into almost completely polarized light by at least one of the two polarizers.

In addition, it is possible to suppress the gap between the polarizers formed of a plurality of sheets from being widened by stacking and bonding a single polarizer without a gap to the polarizers formed of a plurality of sheets. This is because the film that becomes the polarizer expands and contracts due to drying of the polarizer, but by arranging the polarizers in this way, the contact area with the outside world is reduced and the moisture of the polarizer is reduced. This is because it becomes difficult to come off.

In this way, the present inventor has found that it is possible to make it difficult to cause light leakage even on a large screen by arranging the polarizers as described above, and to solve the above-mentioned problems brilliantly. The present inventors have arrived at the present invention by conceiving what can be done.

That is, the present invention is a liquid crystal display device having a front polarizing plate, a liquid crystal panel, and a back polarizing plate in this order from the display surface side, and at least one of the front polarizing plate and the back polarizing plate includes a first polarizer and The first polarizer has a laminated structure including a second polarizer, and the first polarizer includes a single polarizer and includes a region having a lower degree of polarization than the second polarizer. The child is a liquid crystal display device composed of a plurality of polarizers arranged side by side on the same surface.

The present invention is described in detail below.

The liquid crystal display device of the present invention has a front polarizing plate, a liquid crystal panel, and a back polarizing plate in this order from the display surface side. The liquid crystal panel is not particularly limited as long as it includes a liquid crystal layer filled with a liquid crystal material. For example, the liquid crystal panel includes a pair of substrates, and the liquid crystal layer is sandwiched between the pair of substrates. Can be mentioned. Further, by providing electrodes on each of the pair of substrates, an electric field can be formed in the liquid crystal layer, and the orientation of liquid crystal molecules can be controlled based on the strength of the electric field. The polarization state of light transmitted through the liquid crystal layer changes depending on the orientation of the liquid crystal molecules, and is transmitted or blocked by a pair of polarizing plates, a front polarizing plate and a back polarizing plate that sandwich the liquid crystal panel. Can be controlled on and off.

In the present invention, at least one of the front polarizing plate and the rear polarizing plate has a laminated structure including a first polarizer and a second polarizer, and the first polarizer has a region having a low degree of polarization as a second polarization. Contains more than children. That is, in the present invention, the first polarizer has more uneven polarization than the second polarizer. Such unevenness in the degree of polarization occurs when a region having a high degree of polarization and a region having a low degree of polarization are mixed in the polarizer. In this specification, the “region having a low degree of polarization” is a region having a degree of polarization of less than 99.95%, and light transmitted through this region is not converted into sufficient polarization. On the other hand, the “region having a high degree of polarization” is a region having a degree of polarization of 99.95% or more, and light transmitted through this region is converted into sufficient polarization.

In the present invention, the first polarizer is composed of a single polarizer, and the second polarizer is composed of a plurality of polarizers arranged in the same plane. The first polarizer is a single polarizer, and no separator is provided in the same plane. On the other hand, the second polarizer is a polarizer in which a plurality of polarizers are arranged in the same plane, and it is preferable that there is no gap between the polarizers. There may be a slight gap between the polarizers. In the present invention, such a gap is preferably 100 μm or less. In the present invention, the number of polarizers constituting the second polarizer is not particularly limited.

According to such a configuration of the present invention, since the limitation on the degree of polarization of the first polarizer composed of one sheet is relaxed, it is possible to provide a polarizing plate compatible with a large screen, and a plurality of sheets Even if there is a gap in the joint portion of the second polarizer composed of the above, it is possible to obtain a polarizer corresponding to a large screen display without degrading the display quality. By arranging the polarizers in an overlapping manner, it is possible to obtain an effect of suppressing the spread of the interval between the joining portions of a plurality of polarizers, so that the screen size is not limited, and there is no limitation on the manufacturing process such as high-temperature processing. In addition, high-quality display with little display unevenness can be obtained over a long period of time.

The configuration of the liquid crystal display device of the present invention is not particularly limited as long as such components are formed as essential components, and may or may not include other components. Absent. For example, for the first and second polarizers, an optical sheet such as a retardation film for further imparting optical characteristics to the light transmitted through the polarizer may be further disposed. In addition to the first and second polarizers, the front polarizing plate and the rear polarizing plate may include a support film for protecting these polarizers, and the liquid crystal display device is provided on the back side (device) of the back polarizing plate. A light source for displaying an image such as a backlight may be provided on the inner side.

Hereinafter, preferred embodiments of the liquid crystal display device of the present invention will be described.

The second polarizer is preferably disposed closer to the liquid crystal panel than the first polarizer. When light passes through the polarizer, it is converted into polarized light having a vibration direction in the direction of the polarization axis and emitted, but if there is an element that disturbs the polarization axis between the polarizers sandwiching the liquid crystal panel, In some cases, the light travels to the liquid crystal panel with its polarization axis shifted, causing light leakage, and a uniform display cannot be obtained.

Regarding the polarizer, the higher the degree of polarization of the polarizer, the smaller the polarization axis variation. When light passes through a region with a high degree of polarization after passing through a region with a low degree of polarization, the light becomes polarized light having a polarization axis imparted in the region with a high degree of polarization that is transmitted later. After passing through a region with a low degree of polarization, the polarized light that has passed through the region with a high degree of polarization is affected by the region with a low degree of polarization that was transmitted later, resulting in slight variations in the polarization axis. It becomes. Therefore, when the first polarizer and the second polarizer are overlapped, light leakage due to polarization variation is suppressed when the second polarizer including a region with a higher degree of polarization is arranged on the liquid crystal panel side. From the viewpoint of obtaining a uniform display with little unevenness.

In the present invention, even if the polarized light converted by the first polarizer passes through a gap between a plurality of polarizers constituting the second polarizer, the polarization axis varies in the gap region. There is no demerit of arranging the first polarizer and the second polarizer in this order toward the liquid crystal panel with respect to the presence of the gap region.

The front polarizing plate and the back polarizing plate are preferably in a crossed Nicol relationship. In this specification, “in a crossed Nicols relationship” means that the absorption axes of the polarizers of the opposing polarizing plates are substantially orthogonal. The direction of such an absorption axis is determined by the stretching direction of the polarizing film when the polarizer is produced, and the stretching direction is the absorption axis direction. In this specification, the absorption axis is an axis that absorbs light that vibrates in that direction, and the polarization axis is an axis that transmits light that vibrates in that direction. When the polarizing plate is viewed in plan, the polarization axis and the absorption axis are substantially orthogonal. Since the absorption axes of the pair of substrates sandwiching the liquid crystal panel are in a crossed Nicols relationship, for example, when a liquid crystal material having a negative dielectric anisotropy is used as the liquid crystal material, a voltage is applied to the liquid crystal panel. When no is applied, light is blocked by the polarizing plate, and a normally black mode in which no image is displayed is set. In contrast, the front polarizing plate and the back polarizing plate have a parallel Nicol relationship in which the directions of the absorption axes are substantially parallel, and a normally displayed image is displayed when no voltage is applied to the liquid crystal panel. Although the white mode can be considered, the normally black mode is superior in terms of contrast, which is an index of brightness between white display and black display, and a clearer display can be obtained.

When two polarizing plates having absorption axes in a crossed Nicol relationship are manufactured by the same manufacturing method, it may be difficult to obtain a sufficient degree of polarization only with one polarizing plate. This is because the film that becomes the polarizer can secure a sufficient length in the stretching direction, but cannot secure a sufficient width in the direction orthogonal to the stretching direction, and there is a limitation in applying to a large screen. This is because there are cases where the On the other hand, according to the present invention, as described above, it is possible to obtain a polarizer that can cope with an increase in screen size. Therefore, even when the crossed Nicols are arranged in this way, the front polarizing plate and the back polarizing plate Polarizers having a sufficient degree of polarization can be arranged for both, whereby a large-screen liquid crystal display device having high contrast can be obtained.

According to the liquid crystal display device of the present invention, even if it has a large screen, a polarizer having a sufficient degree of polarization can be arranged for both the front and rear polarizing plates. An excellent display in which display unevenness is suppressed can be obtained. In addition, according to the liquid crystal display device of the present invention, it is possible to suppress the gap between the polarizers arranged side by side from being widened, so that excellent display quality can be maintained over a long period of time.

Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited only to these embodiments.

(Embodiment 1)
FIG. 1 is an exploded perspective view schematically showing the configuration of the liquid crystal display device according to the first embodiment. The liquid crystal display device of Embodiment 1 has a large screen, and has a size of 60 inches or more which is generally referred to as a large size. The liquid crystal display device of Embodiment 1 can also be applied to a display having a 108-inch screen size, which is generally referred to as an ultra-large size.

As shown in FIG. 1, the liquid crystal display device 10 of Embodiment 1 has the front polarizing plate 3, the liquid crystal panel 1, and the back polarizing plate 2 in this order from the display surface side. The back polarizing plate 2 includes a first polarizer 22 having a large degree of unevenness in polarization degree (including more regions having a low degree of polarization) and a second element having a small degree of unevenness in polarization degree (including a region having a low degree of polarization). It has a laminated structure including a polarizer 24, and the second polarizer 24 is disposed closer to the liquid crystal panel 1 than the first polarizer 22. Moreover, the 1st polarizer 22 with which the back polarizing plate 2 is provided is comprised with one polarizer, and the 2nd polarizer 24 is comprised with two polarizers arrange | positioned along with the same surface. In the liquid crystal display device 10 of the first embodiment, light (natural light) 100 for performing display travels from the back polarizing plate 2 toward the front polarizing plate 3 and becomes polarized light 200 and is emitted outside the device.

In the first embodiment, the liquid crystal panel 1 includes a pair of substrates 11 and 12 and a liquid crystal layer 13 sandwiched between the pair of substrates 11 and 12. Each of the pair of substrates 11 and 12 includes a support substrate made of glass, resin, and the like, and members such as various wirings that are disposed on the support substrate and perform liquid crystal display. In the first embodiment, such a support substrate is composed of one sheet, and has a large screen size of 60 inches or more.

As an example of the liquid crystal panel 1, one of the pair of substrates is an array substrate 11 and the other is a color filter substrate 12. In the array substrate 11, electrodes for controlling driving of the liquid crystal display are provided on a support substrate. Wiring, semiconductor elements, insulating films, etc. are arranged, and in the color filter substrate 12, an electrode for controlling the driving of liquid crystal display, a resin constituting a colored layer for performing color display, etc. are arranged on the supporting substrate. The form to do is mentioned. In addition, by arranging electrodes on each of the pair of substrates, an electric field can be formed in the liquid crystal layer 13, and the alignment of liquid crystal molecules can be controlled based on the strength of the electric field. Then, the polarization state of the light transmitted through the liquid crystal layer 13 changes depending on the orientation of the liquid crystal molecules, and is transmitted or blocked by the pair of polarizing plates of the front polarizing plate 2 and the back polarizing plate 3 that sandwich the liquid crystal panel 1. Thus, it is possible to control the on / off of the display.

In the first embodiment, the alignment method of the liquid crystal molecules in the liquid crystal layer 13 is not particularly limited, and a TN (Twisted Nematic) method, a VA (Vertical Alignment) method, an IPS (In-Plane Switching) method, or the like can be applied. Therefore, the type of liquid crystal molecules in Embodiment 1 is not particularly limited, such as nematic liquid crystal molecules having negative dielectric anisotropy, nematic liquid crystal molecules having positive dielectric anisotropy, and the like. Just choose.

The liquid crystal display device 10 of Embodiment 1 includes a backlight further on the back side of the back polarizing plate 2, that is, the inside of the device. Examples of the light source of the backlight include a cold cathode tube (CCFL), a light emitting diode (LED), and the like. The arrangement form of the light source is not particularly limited, such as a direct type, a side light (edge light) type, or the like.

FIG. 2 is a schematic cross-sectional view illustrating the laminated structure of the liquid crystal display device of Embodiment 1. In Embodiment 1, the back polarizing plate 2 has PVA films 22 and 24 as a first polarizer and a second polarizer, respectively, TAC films 21 and 23 as films that support these polarizers, and PVA films. 22 and 24 on both sides. That is, in Embodiment 1, the back polarizing plate 2 includes the TAC film 21, the PVA film 22 that is the first polarizer, the TAC film 21, the TAC film 23, the PVA film 24 and the TAC film 23 that are the second polarizer. They are stacked in this order toward the liquid crystal panel 1 side. Moreover, the PVA film 22 which is the first polarizer, and the TAC films 21 on both sides sandwiching the PVA film 22 cover the entire surface with one sheet, and the PVA film which is the second polarizer. 24 and the TAC films 23 on both sides sandwiching the same cover the entire surface with a plurality of sheets on the substrate.

In Embodiment 1, the back polarizing plate 2 is, in other words, a one-piece polarizing plate 14 and a two-piece polarizing plate 15 that are composed of a PVA-based film and TAC films on both sides of the PVA film. Structure. The single-piece polarizing plate 14 and the two-piece polarizing plate 15 are attached to each other using an adhesive. Therefore, such an arrangement has an advantage that it is easy to manufacture.

Thus, in Embodiment 1, since the back polarizing plate 2 has a structure in which the TAC films are sandwiched on both sides of the PVA film, a strong holding effect can be obtained, and the durability of the PVA film is improved and high. An anti-stretching effect can be obtained.

In the first embodiment, the laminated structure of the polarizing plates including the PVA film, the TAC film, etc. is limited to the structure in which the single polarizing plate 14 and the two polarizing plates 15 are directly overlapped as described above. Instead, the following application examples 1 to 3 may be used.

In Embodiment 1, the front polarizing plate 3 has a PVA film 26 as a polarizer, and has TAC films 25 on both sides of the PVA film 26. The polarizer 26 included in the front polarizing plate 3 is a single polarizer and is a polarizer that has less unevenness in the degree of polarization (including less regions with a low degree of polarization). In the first embodiment, when a large screen size is used, only one of the front polarizing plate 3 and the back polarizing plate 2 may be used so that there is little unevenness with a single polarizer. In the case where it is assumed that there is a restriction that cannot be made, and a polarizer with a large screen size and less unevenness can be configured with one sheet, the first polarizer and the second polarization as in the back polarizing plate 2 There is no need to overlap the child.

In the first embodiment, molecules such as iodine complexes and dichroic dyes having different electron densities in the vertical and horizontal directions are adsorbed on the surfaces of the PVA films 22, 24, and 26. The PVA films 22, 24, and 26 are stretched in a certain direction. By stretching in this way, the long axes of the molecules are arranged side by side in the stretching direction, and the vibration direction is in the stretching direction. The light having is absorbed by the molecule. In the first embodiment, PVA-based films are used as the polarizers 22, 24, and 26. However, the polarizers are not particularly limited as long as polarization characteristics can be imparted, and films made of other materials may be used. .

In the first embodiment, a TAC film is used as the support films 21, 23, and 25 disposed on both sides of the polarizers 22, 24, and 26. However, deformation and contraction of the polarizer are suppressed, and the polarizer is fixed. There is no particular limitation as long as it can be used. Examples of the material of the support film 21 include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile and styrene. Examples thereof include styrenic polymers such as polymers (AS resins), polycarbonate polymers, and the like. In addition, polyolefins such as polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers that are ethylene / propylene copolymers, amide polymers such as vinyl chloride polymers, nylons, aromatic polyamides, imide polymers, Sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers A mixture of these polymers may also be used. Furthermore, thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone may be used.

The support films 21, 23, and 25 are preferably made of a material that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and the like. From the viewpoint of having excellent polarization characteristics and durability, a cellulose-based polymer is particularly preferable, and among them, triacetyl cellulose (TAC) having low depolarization (property of breaking polarization) and excellent translucency and durability. ) Is preferred. On the other hand, COP (Cyclo Olefin Polymer: cycloolefin polymer) is preferable from the viewpoint of being excellent in moisture permeability and effective in suppressing the deformation and shrinkage of the polarizer.

The polarizer which comprises the polarizing plate with which the liquid crystal display device of Embodiment 1 is provided is explained in full detail below. FIG. 3 is an exploded plan view schematically illustrating an optical member included in the liquid crystal display device of Embodiment 1. As shown in FIG. 3, the liquid crystal display device of Embodiment 1 includes the polarizer 26 included in the front polarizing plate 3, the second polarizer 24 included in the back polarizing plate 2, and the first polarization from the display surface side. It is comprised including the child 22 in this order. The first polarizer 22 provided in the back polarizing plate 2 is composed of a single polarizer, and the second polarizer 24 is composed of a plurality of polarizers.

As shown in FIG. 3, the absorption axis of the polarizer 26 included in the front polarizing plate 3 is in the horizontal direction, and the absorption axes of the second polarizer 24 and the first polarizer 22 included in the back polarizing plate 2 are in the vertical direction. The respective absorption axes are substantially perpendicular to each other. That is, in Embodiment 1, the front polarizing plate 3 and the back polarizing plate 2 are in a crossed Nicols relationship. Thus, when no voltage is applied to the liquid crystal panel 1 using a liquid crystal material having negative dielectric anisotropy, light is blocked by the polarizing plates 2 and 3 on the front and back sides, and no image is displayed. It can be set to Marie Black mode. As shown in FIG. 3, in Embodiment 1, light (natural light) 100 from the backlight is irradiated from the back polarizing plate 2 toward the front polarizing plate 3 and passes through the back polarizing plate 2 and the front polarizing plate 3. Thus, the polarized light 200 is emitted as display light to the outside of the apparatus.

FIG. 4 is a schematic plan view of the first polarizer included in the back polarizing plate in the first embodiment. In FIG. 4, the darker portion is the region 22a having a higher degree of polarization, and the lighter portion is the region 22b having a lower degree of polarization. As shown in FIG. 4, the first polarizer 22 provided in the back polarizing plate 2 in the first embodiment is composed of a single polarizer. That is, in the range corresponding to the display area, the first polarizer 22 is not provided with a gap, and is formed of a single film. Therefore, an area of 60 inches or more per polarizer is provided. Have. In the first embodiment, the first polarizer 22 may be formed of a film having a large degree of polarization unevenness. That is, a region having a low degree of polarization may partially exist. In the first embodiment, the ratio of the region where the degree of polarization present in the first polarizer 22 is 99.95% or more is 50% or more and less than 95% with respect to the area per polarizer, and the degree of polarization is Less than 99.95% of the area occupies the remaining area. Thus, a large screen size polarizer can be obtained in the form of a single sheet by not strictly determining uniformity in the degree of polarization of the polarizer.

FIG. 5 is a schematic plan view of a second polarizer included in the back polarizing plate in the first embodiment. As shown in FIG. 5, the second polarizer 24 provided in the back polarizing plate 2 in Embodiment 1 is composed of a plurality of polarizers arranged side by side on the same plane. That is, in the range corresponding to the display region, the second polarizer 24 is composed of a plurality of polarizers joined together to form a single polarizer, whereby the entire area of the second polarizer 24 is 60 inches or more. have. A gap having a certain width may be provided between the polarizers constituting the second polarizer 24 in the first embodiment. Thus, by limiting the number of polarizers to one, it is possible to obtain a large screen size polarizer with little unevenness in polarization. In the first embodiment, the number of polarizers constituting the second polarizer 24 is two. However, the number is not particularly limited, and the number of polarizers is not limited to four according to the screen size. It may be a sheet and may be adjusted as appropriate. Furthermore, although the polarizer which comprises the 2nd polarizer 23 in Embodiment 1 is supposed to bisect the long side of the 2nd polarizer 23, even if it bisects the short side In addition, both the long side and the short side may be divided into two equal parts, and the number of the equal parts is not limited. In addition, it is not always necessary to distribute a plurality of polarizers evenly, and the layout can be changed as appropriate. In the first embodiment, in the second polarizer 24, a region having a polarization degree of 99.95% or more occupies 95% or more of the area per polarizer.

FIG. 6 is a schematic plan view showing the first polarizer and the second polarizer constituting the back polarizing plate in the first embodiment. (A) is a schematic plan view of the first polarizer, (b) is a schematic plan view of the second polarizer, and (c) is a stack of the first polarizer and the second polarizer. It is a plane schematic diagram at the time. As shown in FIG. 6, in the first embodiment, the back polarizing plate 2 is configured by superimposing such a first polarizer 22 and a second polarizer 24. By forming a single polarizer by superimposing a first polarizer 22 composed of a single sheet and a second polarizer 24 composed of a plurality of sheets with little variation in polarization degree, A single polarizing plate 27 with little unevenness in polarization degree can be formed. Such a polarizing plate 27 eliminates problems such as enlargement of the screen, generation of display unevenness, and generation of bright lines in the joining region, which are generated by using any one of these, and a display screen having a large screen size. Even if it is, it is possible to obtain good display quality, and further, it is possible to suppress the occurrence of such problems over a long period of time without any limitation of the manufacturing process such as high-temperature treatment.

(Application 1)
FIG. 7 is a schematic cross-sectional view showing an application example 1 of the back polarizing plate of the first embodiment. In the first embodiment, the structure of the polarizing plate may be configured as described above in order to simplify the structure of the polarizing plate configured using two types of polarizers.

As shown in FIG. 7, in the polarizing plate 102 of the application example 1, the TAC films 121, 123, and 125 are arranged on both sides of the PVA films 122 and 124, but the PVA film and a pair of TACs that sandwich the TAC films. Unlike the form in which two polarizing plates composed of films are simply overlapped, only one TAC film 123 is disposed between the two PVA films 122 and 124. That is, in Application Example 1, the polarizing plate 102 includes the TAC film 121, the PVA film (first polarizer) 122, the TAC film 123, the PVA film (second polarizer) 124, and the TAC film 125 on the liquid crystal panel 1 side. They are stacked in this order. Moreover, the PVA-type film 122 which is a 1st polarizer, and the TAC film 121 arrange | positioned under it (backlight side) cover the whole surface with one sheet | seat with respect to a board | substrate, The PVA film 124 as a child and the TAC films 123 and 125 on both sides sandwiching the PVA film 124 cover the entire surface of the substrate with a plurality of sheets.

According to the arrangement form of the application example 1, the structure is thinner than the structure in which the single polarizing plate 14 and the two polarizing plates 15 are directly overlapped as shown in FIG. The entire plate can be made thin. Moreover, since the TAC film can be reduced by one sheet, the cost of the material can be reduced and the transmittance can be improved. Furthermore, even in such a laminated structure, since the TAC film is arranged on both sides of the PVA-based film, a high holding effect can be obtained, and the durability of the PVA-based film can be improved and a high anti-stretching effect can be obtained. Obtainable.

(Application example 2)
FIG. 8 is a schematic cross-sectional view showing an application example 2 of the back polarizing plate of the first embodiment. In the first embodiment, the structure of the polarizing plate may be configured as described above in order to simplify the structure of the polarizing plate configured using two types of polarizers.

As shown in FIG. 8, in the polarizing plate of application example 2, TAC films are arranged on both sides of the PVA film, but like the polarizing plate of application example 1, a PVA film and a pair of TACs sandwiching the PVA film. Unlike the form in which two polarizing plates composed of films are simply overlapped, only one TAC film 223 is arranged between the two PVA films 222 and 224. That is, in the application example 2, the polarizing plate 202 includes the TAC film 221, the PVA film (first polarizer) 222, the TAC film 223, the PVA film (second polarizer) 224, and the TAC film 225 on the liquid crystal panel 1 side. They are stacked in this order. Further, the PVA film 222 as the first polarizer and the TAC films 221 and 223 on both sides sandwiching the PVA film 222 cover the entire surface with one sheet, and the PVA as the second polarizer. The system film 224 and the TAC film 225 disposed thereon (on the liquid crystal layer side) cover the entire surface with a plurality of sheets on the substrate.

According to the arrangement form of the application example 2, since the structure is thinner than the structure in which the single polarizing plate 14 and the two polarizing plates 15 are directly overlapped as shown in FIG. The entire plate can be made thin. Moreover, since the TAC film can be reduced by one sheet, the cost of the material can be reduced and the transmittance can be improved. Furthermore, even in such a laminated structure, since the TAC film is arranged on both sides of the PVA-based film, a high holding effect can be obtained, and the durability of the PVA-based film can be improved and the high stretch prevention effect can be obtained. Obtainable. In addition, according to the application example 2, unlike the application example 1, the surface of the PVA film 223 as the first polarizer is exposed to the outside through a gap of the PVA film 224 as the second polarizer. Therefore, a higher protective effect can be given to the PVA film 223 that is the first polarizer.

(Application 3)
FIG. 9 is a schematic cross-sectional view showing an application example 3 of the back polarizing plate of the first embodiment. In the first embodiment, the structure of the polarizing plate may be configured as described above in order to simplify the structure of the polarizing plate configured using two types of polarizers.

As shown in FIG. 9, the polarizing plate of the application example 3 has a configuration in which no TAC film is interposed between the PVA film 322 as the first polarizer and the PVA film 324 as the second polarizer. Yes, that is, in Application Example 3, the polarizing plate is a TAC film 321, a PVA film (first polarizer) 322, a PVA film (second polarizer) 324, and a TAC film 323 toward the liquid crystal panel 1 side. They are stacked in order. Moreover, the PVA film 322 that is the first polarizer and the TAC film 321 disposed below (backlight side) cover the entire surface with one sheet on the substrate. The PVA film 324 as a child and the TAC film 323 arranged on the liquid crystal layer side cover the entire surface with a plurality of sheets on the substrate.

According to the arrangement form of the application example 3, the holding effect of the PVA film is slightly inferior to that of the application example 1 and the application example 2. However, as shown in FIG. Since the structure is much thinner than the structure in which the polarizing plate 15 as a product is directly overlapped, the entire polarizing plate can be greatly thinned. In addition, since a plurality of TAC films can be reduced, the cost of the material can be reduced, and the transmittance is greatly improved. In Application Example 3, a TAC film is not disposed between the PVA film 322 that is the first polarizer and the PVA film 324 that is the second polarizer. Since the TAC films 321 and 323 are arranged one by one, the holding effect of the PVA films 322 and 324 can be sufficiently obtained.

(Embodiment 2)
FIG. 10 is a schematic diagram illustrating a configuration of the liquid crystal display device according to the second embodiment. (A) is a disassembled perspective view, (b) is sectional drawing. As shown in FIG. 10, the liquid crystal display device 20 of Embodiment 2 includes a first polarizer 36 having a large degree of polarization degree unevenness (including more regions having a low degree of polarization) and a degree of polarization in the front polarizing plate 5. The back polarizing plate 4 has a non-uniformity in the degree of polarization (including a region with a low degree of polarization). Except having the single-piece polarizing plate provided with the polarizer 32, it is the same as that of Embodiment 1. FIG. That is, in the liquid crystal display device 20 of Embodiment 2, the laminated structure of the first polarizer and the second polarizer of the present invention is used for the front polarizing plate 5 instead of the back polarizing plate 4. In the liquid crystal display device 20 according to the second embodiment, light (natural light) 100 from the backlight for display travels from the back polarizing plate 4 toward the front polarizing plate 5, and becomes polarized light 200. It is emitted outside the device.

In Embodiment 2, the liquid crystal display device 20 has the front polarizing plate 5, the liquid crystal panel 1, and the back polarizing plate 4 in this order from the display surface side. In Embodiment 2, the front polarizing plate 5 has a laminated structure including the first polarizer 36 and the second polarizer 34, and the second polarizer 34 is more liquid crystal panel 1 than the first polarizer 36. Arranged on the side.

More specifically, in the second embodiment, the front polarizing plate 5 has PVA films 36 and 34 as a first polarizer and a second polarizer, respectively, and TAC films 35 and 33 as films that support these polarizers. And PVA films 36 and 34 on both sides. That is, in Embodiment 2, the front polarizing plate 5 includes the TAC film 35, the PVA film 36 that is the first polarizer, the TAC film 35, the TAC film 33, the PVA film 34 and the TAC film 33 that are the second polarizer. They are stacked in this order toward the liquid crystal panel 1 side. Moreover, the PVA film 36 which is the first polarizer, and the TAC films 35 on both sides sandwiching the PVA film 36 cover the entire surface with one sheet, and the PVA film which is the second polarizer. 34 and the TAC films 33 on both sides sandwiching the same cover the entire surface with a plurality of sheets on the substrate.

In Embodiment 2, the back polarizing plate 4 has a PVA film 32 as a polarizer, and has TAC films 31 on both sides of the PVA film 32.

In such a form, the surface polarizing plate 5 has the same characteristics as a single polarizing plate with little unevenness in the degree of polarization, so that even if the display screen has a large screen size, the display quality is good. Therefore, it is possible to maintain a good display over a long period of time without limitation of a manufacturing process such as high-temperature treatment.

In the second embodiment, the laminated structure of the polarizing plates including these PVA film, TAC film and the like may be configured as in the above application examples 1 to 3, and the above-described effects can be obtained for each.

(Embodiment 3)
FIG. 11 is a schematic diagram illustrating a configuration of the liquid crystal display device according to the third embodiment. (A) is a disassembled perspective view, (b) is sectional drawing. As shown in FIG. 11, the liquid crystal display device 30 according to the third embodiment includes a first polarizer that has a large degree of unevenness in the degree of polarization (including more regions having a low degree of polarization) in both the front polarizing plate and the back polarizing plate. 42 and 48, and the same structure as that of the first embodiment except that the second polarizers 44 and 46 include the second polarizers 44 and 46 with less unevenness of the polarization degree (including less regions with low polarization degree). . That is, the liquid crystal display device 30 of Embodiment 3 is a form in which the laminated structure of the first polarizer and the second polarizer of the present invention is used for both the front polarizing plate 7 and the back polarizing plate 6. In the liquid crystal display device 30 according to the third embodiment, light (natural light) 100 from a backlight for performing display travels from the back polarizing plate 2 toward the front polarizing plate 3, and becomes polarized light 200. It is emitted outside the device.

In Embodiment 3, the liquid crystal display device 30 has the front polarizing plate 7, the liquid crystal panel 1, and the back polarizing plate 6 in this order from the display surface side. In Embodiment 3, the front polarizing plate 7 has a laminated structure including a first polarizer 48 and a second polarizer 46, and the second polarizer 46 is more liquid crystal panel 1 than the first polarizer 48. Arranged on the side. Furthermore, in Embodiment 3, the back polarizing plate 6 has a laminated structure including a first polarizer 42 and a second polarizer 44, and the second polarizer 44 is more liquid crystal panel 1 than the first polarizer 42. Arranged on the side.

More specifically, in Embodiment 3, the back polarizing plate 6 has PVA- type films 42 and 44 as the first polarizer and the second polarizer, respectively, and the TAC films 41 and 43 as films that support these polarizers. And PVA films 42 and 44 on both sides. That is, in Embodiment 3, the back polarizing plate 6 includes the TAC film 41, the PVA film 42 that is the first polarizer, the TAC film 41, the TAC film 43, the PVA film 44 and the TAC film 43 that are the second polarizer. They are stacked in this order toward the liquid crystal panel 1 side. Further, the PVA film 42 as the first polarizer and the TAC films 41 on both sides sandwiching the PVA film cover the entire surface with one sheet, and the PVA film as the second polarizer. 44 and the TAC films 43 on both sides sandwiching the same cover the entire surface with a plurality of sheets on the substrate.

Further, in Embodiment 3, the front polarizing plate 7 has PVA films 48 and 46 as the first polarizer and the second polarizer, respectively, and the TAC films 47 and 45 as the films for supporting these polarizers, It is provided on both sides of each of the system films 48 and 46. That is, in Embodiment 1, the front polarizing plate 7 includes the TAC film 47, the PVA film 48 that is the first polarizer, the TAC film 47, the TAC film 45, the PVA film 46 and the TAC film 45 that are the second polarizer. They are stacked in this order toward the liquid crystal panel 1 side. Moreover, the PVA film 48 which is the first polarizer and the TAC films 47 on both sides sandwiching the PVA film cover the entire surface with a single sheet, and the PVA film which is the second polarizer. 46 and the TAC films 45 on both sides sandwiching the same cover the entire surface with a plurality of sheets on the substrate.

Even in such a form, the front polarizing plate 3 and the back polarizing plate 2 have the same characteristics as a single polarizing plate with little unevenness in the degree of polarization. Even in such a case, it is possible to obtain a good display quality, and it is possible to maintain a good display over a long period of time without limitation of a manufacturing process such as a high temperature treatment.

In the third embodiment, the laminated structure of the polarizing plates including these PVA film, TAC film and the like may be configured as in the above application examples 1 to 3, and the above effects can be obtained for each.

(Embodiment 4)
FIG. 12 is a schematic diagram illustrating a configuration of the liquid crystal display device of the fourth embodiment. (A) is a disassembled perspective view, (b) is sectional drawing. As shown in FIG. 12, the liquid crystal display device 40 of Embodiment 4 includes a second polarizer 54 with less unevenness in the degree of polarization (including a region with a lower degree of polarization) in the back polarizing plate 8, and the degree of polarization. This is the same as in the first embodiment except that the first polarizer 52 having a large unevenness (including more regions having a low degree of polarization) is arranged in this order toward the liquid crystal panel 1. That is, the liquid crystal display device 40 of Embodiment 4 is a mode in which the laminated structure of the first polarizer and the second polarizer is used for the back polarizing plate, but the arrangement order of the first polarizer and the second polarizer is the same. This is the reverse of the arrangement order of the first embodiment. In the fourth embodiment, the light (natural light) 100 from the backlight for performing the display travels from the back polarizing plate 2 toward the front polarizing plate 3, and becomes polarized light 200 and is emitted outside the apparatus. The

More specifically, in the fourth embodiment, the back polarizing plate 8 includes PVA films 52 and 54 as the first polarizer and the second polarizer, respectively, and the TAC films 51 and 53 as films that support these polarizers. And PVA films 52 and 54 on both sides. That is, in Embodiment 1, the back polarizing plate 8 includes the TAC film 53, the PVA film 54 as the second polarizer, the TAC film 53, the TAC film 51, the PVA film 52 and the TAC film 51 as the first polarizer. They are stacked in this order toward the liquid crystal panel 1 side. Moreover, the PVA film 52 which is the first polarizer, and the TAC films 51 on both sides sandwiching the PVA film 52 cover the entire surface with a plurality of sheets, and the PVA film which is the second polarizer. 54 and the TAC films 53 on both sides sandwiching the same cover the entire surface with one sheet.

In Embodiment 2, the front polarizing plate 9 has a PVA film 56 as a polarizer, and has TAC films 55 on both sides of the PVA film 56.

In such a configuration, the light (natural light) 100 from the backlight passes through the second polarizer and then passes through the first polarizer. Therefore, after the light passes through the first polarizer, Although it is inferior in terms of the effect of improving the display characteristics as compared with Embodiments 1 to 3 in which the polarizer is transmitted, the polarization characteristics of the back polarizing plate 2 are significantly larger than when the first polarizer or the second polarizer is used alone. Therefore, even if it is a display screen of a large screen size, it is possible to obtain a good display quality, and it is possible to maintain a good display over a long period of time without limitation of a manufacturing process such as high-temperature processing. .

In Embodiment 4, the laminated structure of the polarizing plates including these PVA film, TAC film and the like may be configured as in the above application examples 1 to 3, and the above-described effects can be obtained for each.

The present application claims priority based on the Paris Convention or the laws and regulations in the country to which the transition is based on Japanese Patent Application No. 2008-160043 filed on June 19, 2008. The contents of the application are hereby incorporated by reference in their entirety.

1 is an exploded perspective view schematically showing a configuration of a liquid crystal display device of Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view illustrating a stacked structure of the liquid crystal display device of Embodiment 1. 3 is an exploded plan view schematically showing an optical member provided in the liquid crystal display device of Embodiment 1. FIG. 2 is a schematic plan view of a first polarizer included in a back polarizing plate in Embodiment 1. FIG. 3 is a schematic plan view of a second polarizer provided in the back polarizing plate in Embodiment 1. FIG. 2 is a schematic plan view showing a first polarizer and a second polarizer that constitute a back polarizing plate in Embodiment 1. FIG. (A) is a schematic plan view of the first polarizer, (b) is a schematic plan view of the second polarizer, and (c) is a stack of the first polarizer and the second polarizer. It is a plane schematic diagram at the time. 3 is a schematic cross-sectional view showing Application Example 1 of the back polarizing plate of Embodiment 1. FIG. 6 is a schematic cross-sectional view showing an application example 2 of the back polarizing plate of Embodiment 1. FIG. 6 is a schematic cross-sectional view showing Application Example 3 of the back polarizing plate of Embodiment 1. FIG. 6 is a schematic diagram illustrating a configuration of a liquid crystal display device of Embodiment 2. FIG. (A) is a disassembled perspective view, (b) is sectional drawing. 6 is a schematic diagram illustrating a configuration of a liquid crystal display device of Embodiment 3. FIG. (A) is a disassembled perspective view, (b) is sectional drawing. 6 is a schematic diagram illustrating a configuration of a liquid crystal display device of Embodiment 4. FIG. (A) is a disassembled perspective view, (b) is sectional drawing.

Explanation of symbols

1: Liquid crystal panels 2, 4, 6: Back polarizing plates 3, 5, 7: Front polarizing plates 10, 20, 30, 40: Liquid crystal display device 11: Array substrate 12: Color filter substrate 13: Liquid crystal layers 21, 23 25, 31, 33, 35, 41, 43, 45, 47, 51, 53, 55, 121, 123, 125, 221, 223, 225, 321, 323: support film, TAC film 22, 36, 42, 48 , 52, 122, 222, 322: From the first polarizer, PVA film 24, 26, 32, 34, 44, 46, 54, 56, 124, 224, 324: From the second polarizer, PVA film 22a: High polarization degree region 22b: Lower polarization degree region 27: Pseudo-polarized single polarizing plate 100: Light from backlight (natural light)
102, 202, 302: Polarizing plate 200: Polarized light

Claims (3)

1. From the display surface side, a liquid crystal display device having a front polarizing plate, a liquid crystal panel and a back polarizing plate in this order,
   At least one of the front polarizing plate and the back polarizing plate has a laminated structure including a first polarizer and a second polarizer,
   The first polarizer is composed of a single polarizer and includes more regions with a lower degree of polarization than the second polarizer.
   The liquid crystal display device, wherein the second polarizer is composed of a plurality of polarizers arranged side by side on the same plane.
2. The liquid crystal display device according to claim 1, wherein the second polarizer is disposed closer to the liquid crystal panel than the first polarizer.
3. The liquid crystal display device according to claim 1, wherein the front polarizing plate and the back polarizing plate are in a crossed Nicols relationship.

Images