JP6669541B2 - Liquid crystal display - Google Patents

Description

  The present invention is a display device mounted on an automobile, an aircraft, a ship, and the like, a smartphone, a tablet terminal, a portable game device, a mobile device such as a digital camera, and a digital signage installed in a public space, a store of a commercial facility, and the like. The present invention relates to a liquid crystal display device used as an image display device of other devices, and particularly to a liquid crystal display device having an injection molded panel formed by injection molding.

In recent years, as applications of liquid crystal display devices, those used outdoors are increasing, for example, display devices mounted on automobiles, aircraft, ships, etc., smartphones, tablet terminals, mobile devices such as digital cameras for portable game devices, and even more. Examples include digital signage installed in public spaces and commercial facilities.
In many liquid crystal display devices used outdoors, a cover material (also referred to as a “front panel” or “front panel”) is attached to the viewing surface for the purpose of preventing damage and damage.

As a material of such a cover material, a glass material such as a tempered glass has been conventionally used, but in recent years, a plastic material has been used due to advantages such as reduction in weight and prevention of cracking.
For example, Patent Literature 1 discloses a resin laminate in which a hard coat layer is laminated on a laminate obtained by co-extruding a polycarbonate resin and an acrylic resin.
In addition, Patent Document 2 discloses a laminated extruded resin plate for a touch panel that is hardly scratched on the surface and that is relatively easy to manufacture. An acrylic resin layer is formed by coextrusion molding on at least the surface to be touched of the polycarbonate resin layer. A laminated extruded resin plate for a touch panel characterized by being laminated is disclosed.

As described above, since the number of liquid crystal display devices used outdoors is increasing, the chances of wearing polarized sunglasses and viewing the display screen of the liquid crystal display device are also increasing.
Many liquid crystal display devices have a linear polarizing plate on the viewing side. In such a liquid crystal display device, an observer sees linearly polarized light emitted from the polarizing plate. When the display screen is observed while wearing the camera, various problems may occur in the positional relationship between the absorption axis of the polarizing plate on the viewing side of the liquid crystal display device and the absorption axis of the sunglasses. For example, when a member having a phase difference is not interposed between the polarizing plate on the viewing side of the liquid crystal display device and the polarizing sunglasses of the observer, it is completely determined that the absorption axes of these polarizing plates and polarizing sunglasses are orthogonal to each other. You will not be able to see it. Also, even if a cover material or the like having a phase difference is interposed therebetween, depending on the positional relationship between the two polarization axes, the screen may be darkened, undesired coloring may occur, interference colors may be seen, and the like. In some cases, the display could not be recognized.

  For this reason, Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2005-157082) discloses a conventional display device that can prevent variations in display such as coloring and uneven shading depending on locations even when observation is performed through a polarizing plate such as polarized sunglasses. A display element having a polarizing plate at the forefront, disposed in front of the display element, a translucent cover having an in-plane retardation, and disposed between the polarizing plate and the translucent cover, There has been proposed a display device having a translucent optical element having an in-plane retardation, which reduces the influence of the retardation of the translucent cover on human visibility.

  Further, in order to provide a liquid crystal display device which can ensure highly excellent visibility regardless of an observation angle when a screen is observed through a polarizing plate such as sunglasses, Japanese Patent Application Laid-Open No. 2012-230390. In the liquid crystal display device having at least a backlight light source, a liquid crystal cell, and a polarizing plate disposed on the viewing side of the liquid crystal cell, a white light emitting diode is used as the backlight light source, and the polarizing plate is visually recognized. A polymer film having a retardation of 3000 to 30000 nm on the side, wherein an angle between the absorption axis of the polarizing plate and the slow axis of the polymer film is arranged to be about 45 degrees and used. A method for improving the visibility of a liquid crystal display device has been proposed.

JP 2006-103169 A JP 2010-182263 A JP 2005-157082 A JP 2012-230390 A

  If the cover material used for the liquid crystal display device as described above can be formed by injection molding, it can be easily manufactured even in a form having a special shape such as an opening or a curved portion. However, when this type of plastic cover material is injection-molded, orientation occurs in the flow direction of the molding resin, and a phase difference having an optical axis in the flow direction of the resin occurs. In addition, since the flow of the resin in the molding die is not uniform, the resin often has various orientation angles and various phase differences depending on locations in the injection molded member. In particular, when the cover material has a portion having a different thickness, or has a curved surface shape or another three-dimensional shape, there is a large phase difference variation near the gate, a peripheral portion having a different thickness or shape, and the like. And the visibility when wearing polarized sunglasses is significantly deteriorated.

  As described above, since the injection molded member has a large phase difference and various directions of the phase difference, the liquid crystal display device having the injection molded panel on the viewing side of the polarizing plate is disclosed in Patent Documents 3 and 4 and the like. Polymer film, that is, a polymer film having a phase difference of 3000 to 30000 nm, so that the angle between the absorption axis of the polarizing plate and the slow axis of the polymer film is approximately 45 degrees. There was a problem that it was difficult to improve the visibility by simply arranging them.

  Therefore, an object of the present invention is to provide a liquid crystal display device having an injection molded panel on the viewing side of a polarizing plate, which can ensure visibility even when polarized sunglasses are worn and observed. It is in.

The present invention includes an image display area when viewed from the viewing side, a liquid crystal cell (A), a polarizing plate (B) disposed on the viewing side of the liquid crystal cell (A), and a continuous emission spectrum. And a backlight light source (C) having:
Injection molded panel (D) is arranged on the viewing side of polarizing plate (B), and retardation film (E) is arranged between polarizing plate (B) and injection molded panel (D),
The retardation film (E) has an in-plane retardation (ReE) satisfying the following expression (1), and the difference between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B). Arranged so that the angle between them is 35-55 °, and
The in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection-molded panel (D) in the image display area have the following relationship (2). A liquid crystal display device is proposed.
(1) 3000 nm <ReE ≦ 100000 nm
(2) ReE-ReD ≧ 3000 nm

The present invention also includes an image display area when viewed from the viewing side, and includes a liquid crystal cell (A), a polarizing plate (B) disposed on the viewing side of the liquid crystal cell (A), and continuous light emission. A backlight light source (C) having a spectrum,
A laminated panel member (F) having an injection molded panel (D) is arranged on the viewing side of the polarizing plate (B), and a retardation film (E) is interposed between the polarizing plate (B) and the laminated panel member (F). )
The retardation film (E) has an in-plane retardation (ReE) satisfying the following expression (1), and the difference between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B). Arranged so that the angle between them is 35-55 °, and
The in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReF) of the laminated panel member (F) in the image display area have the following relationship (3). A liquid crystal display device is proposed.
(1) 3000 nm <ReE ≦ 100000 nm
(3) ReE-ReF ≧ 3000 nm

  In any of the liquid crystal display devices proposed by the present invention, in a liquid crystal display device having an injection molded panel on the viewing side of a polarizing plate, visibility can be prevented from deteriorating due to a phase difference of the injection molded panel, and polarized sunglasses are worn. The visibility can be ensured even when observed by viewing. Moreover, the configuration can be made without deteriorating the design.

FIG. 2 is a plan view of an example of the liquid crystal display device of the present invention as viewed from the viewing side. FIG. 1 is a side sectional view showing an example of a liquid crystal display device of the present invention in an exploded state. FIG. 5 is a side sectional view showing another example of the liquid crystal display device of the present invention in an exploded state. FIG. 10 is a side sectional view showing another example of the liquid crystal display device of the present invention in an exploded state. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed an example of the injection molding panel which comprises the liquid crystal display device of this invention, (a) is the sectional side view, (b) is the perspective view at the time of seeing from a visual recognition side.

  Next, the present invention will be described based on embodiments. However, the present invention is not limited to the embodiment described below.

<This liquid crystal display>
As shown in FIG. 1, a liquid crystal display device according to an example of an embodiment of the present invention (referred to as “the present liquid crystal display device”) has an image display area 1 and an image non-display area 2 when viewed from the viewer side. And a liquid crystal cell (A), a polarizing plate (B) arranged on the viewing side of the liquid crystal cell (A), and a backlight light source (C), as shown in FIG. At the same time, an injection molded panel (D) as a front panel is disposed on the viewing side of the polarizing plate (B), and a retardation film (E) is provided between the polarizing plate (B) and the injection molded panel (D). This is a liquid crystal display device having a configuration of being arranged.
The image display area 1 is an area where an image is displayed, and the image non-display area 2 is an area where an image is not displayed (for example, a printed area).

  Note that the present liquid crystal display device only needs to have at least the above-described configuration, and may include another member. For example, as shown in FIG. 3, the functional film (G) may constitute a laminated panel member (F) in which the functional film (G) is arranged without using an adhesive or an adhesive, or as shown in FIG. A laminated panel member (F) in which a functional film (G) having various necessary functions is integrated with the injection molded panel (D) via an adhesive or an adhesive may be used. The other members are not limited to the functional film (G) described later.

<Liquid crystal cell (A)>
The configuration of the liquid crystal cell (A) itself is not limited as long as the polarizing plate (B) is arranged at least on the viewing side. As an example, there can be mentioned a liquid crystal cell by a driving method such as a TN type, a VA type, and an IPS type which are currently widely used as active matrix driving.

<Polarizing plate (B)>
The polarizing plate (B) is a linear polarizing plate disposed on the viewing side of the liquid crystal cell (A).
The material and configuration of the polarizing plate (B) are arbitrary. For example, a film obtained by laminating a TAC (triacetyl cellulose) film as a protective film on a stretched polyvinyl alcohol film using iodine as an alignment dye has been widely put into practical use as this type of polarizing plate.
Further, the polarizing plate (B) may have a layer structure having a hard coat having substantially no retardation on its surface and having functions such as antiglare, low reflection, and antistatic.

  The polarizing plate may be provided only on the viewing side of the liquid crystal cell (A), or may be provided on both sides of the liquid crystal cell (A).

<Backlight light source (C)>
The backlight light source (C) has a continuous emission spectrum from the viewpoint of enjoying the effects of the present invention.
When the backlight light source (C) is a set of monochromatic lights having a narrow half width such as a cold cathode tube, for example, even if the phase difference of the retardation film (E) is sufficiently large, the bias remains in the transmitted light. Since the interference color does not disappear, it is difficult to enjoy the effects of the present invention. On the other hand, in the case of continuous light having a continuous emission spectrum, such as a white LED, if the retardation of the retardation film (E) is sufficiently large, a good image without interference colors can be visually recognized. Thus, the effects of the present invention can be effectively enjoyed.

  Here, “continuous emission spectrum” means light that does not separate into individual line spectra when viewed with a spectroscope, and that produces a spectrum that is continuously broadened with respect to wavelength, and is preferably a visible light wavelength. The spectrum includes all light of any wavelength in the range. For example, the emission spectrum of a light emitting diode (LED), an electroluminescence panel, etc. is a continuous emission spectrum, whereas the emission spectrum of a cold cathode tube, a hot cathode, etc. is not a continuous emission spectrum.

  The method and configuration of disposing the backlight light source (C) may be the same as those of the conventional liquid crystal display device, and any configuration can be adopted. For example, in the case of an edge light source, light is guided to a liquid crystal cell via a backlight unit including a reflection sheet, a light guide plate, a diffusion plate, a prism sheet, a brightness enhancement film, and the like.

<Injection molding panel (D)>
The injection-molded panel (D) is an injection-molded panel body, which includes a sheet-shaped or plate-shaped member, a curved surface shape, and a member exhibiting another three-dimensional shape. Here, the three-dimensional shape intends a shape having a Z axis (height, standing wall, or the like).
In general, injection-molded members often have various values of phase difference depending on the location, and have characteristics of having various orientation axes depending on the shape.

  The phase difference of the injection-molded panel (D) depends on the shape and injection conditions of the molded panel, and it is possible to set the shape and injection conditions so that there is almost no phase difference in the display area. However, inconveniences often occur, such as the degree of freedom in panel design is impaired, or unfavorable injection conditions must be set.

  Regions where the phase difference is likely to be high or where the alignment direction is likely to vary include the vicinity of the gate, the periphery of the opening, the vicinity of a portion having a different thickness, and also a liquid crystal panel having a non-rectangular shape such as a circular shape or a heart shape. Examples include the end of a molded panel. In such an area, in general, the phase difference often becomes 350 nm or more, which causes remarkable coloring due to interference at the time of crossed Nicols observation, and it is necessary to consider a panel design so that the area is not used as a display area.

  Further, in order to reduce the developed phase difference, it is necessary to adjust various injection conditions such as a gate shape and a position, an injection temperature, an injection speed, a mold temperature, and a holding pressure. However, in some cases, other problems such as thermal deterioration of resin, sink marks, short shots, weld lines, etc. may occur.To avoid these problems, a great deal of effort is required, such as reviewing the mold design and setting injection conditions. And

The present invention can avoid such inconveniences. For example, by expanding the display area of the present liquid crystal display device, it is possible to increase the degree of freedom in design, and the present invention can be applied to emission conditions. It is possible to enjoy the advantage that the possible range can be expanded.
In view of the above, it is preferable that the present invention be applied to the case where the in-plane phase difference maximum value (ReD) of the injection-molded panel (D) in the image display region is 350 nm to 5000 nm.
Regarding the injection molded panel (D), the maximum value of the in-plane retardation of each part is not defined as the average value of the in-plane retardation of each part as described above. This is because there may be various values of phase difference depending on the location due to the nature of.
In order to adjust the in-plane phase difference maximum value (ReD) of the injection molded panel (D) to the above range, the injection temperature, the injection speed, and the mold temperature are optimum for the shape of the injection molded panel (D) and the resin to be injected. It is preferable to adjust the injection conditions such as the holding pressure. However, it is not limited to such a method.

The present invention can be applied to the case where the in-plane phase difference maximum value (ReD) of the injection molded panel (D) in the image display area is less than 350 nm, but this area is affected by interference during observation under orthogonal Nicols. Even if coloring is not so remarkable and the orientation axis is oriented in various directions, the improvement effect of the present invention is not so remarkable. Therefore, the present invention is preferably applied to a case where the in-plane phase difference maximum value (ReD) of the injection-molded panel (D) in which coloring due to interference is noticeable is 350 nm or more.
If the maximum value (ReD) of the in-plane phase difference of the injection molded panel (D) in the image display area is in this area, the image quality of the display device is dramatically improved. If the maximum in-plane retardation value (ReD) of the injection molded panel (D) is larger than 5000 nm, the residual strain during molding is large, and the molded product is likely to be warped or deformed, and in some cases, stress cracks may occur. And other disadvantages occur.
From such a viewpoint, the maximum in-plane retardation value (ReD) of the injection-molded panel (D) in the image display region is preferably from 350 nm to 5000 nm, and more preferably from 400 nm to 4000 nm.

  The resin material constituting the injection molded panel (D) is not particularly limited as long as it is a transparent thermoplastic resin. For example, a material having, as a base resin, one or a mixture of two or more selected from the group consisting of polycarbonate, acrylic resin, polyester, polyethylene, polypropylene, cyclic olefin resin, styrene resin, and vinyl chloride resin. Can be. Among them, polycarbonate, acrylic resin, polyester and the like can be preferably exemplified from the viewpoints of transparency and ease of molding. Above all, in a front panel used for a touch panel display for an in-vehicle device, a material using polycarbonate as a base resin is preferable from the viewpoint of scattering prevention.

  As the polyester resin, from the viewpoint of transparency, moldability, etc., a low-crystalline polyester resin is preferable.For example, a copolymer in which a part of the acid component of polyethylene terephthalate is replaced with isophthalic acid or the like, or a glycol component A copolymer in which a part of is replaced with 1.4-cyclohexanedimethanol or the like is preferable.

  As the polycarbonate, for example, aromatic polycarbonate, aliphatic polycarbonate, and aromatic aliphatic polycarbonate can also be used, and are not limited to general polycarbonates containing bisphenol A as a main raw material. For example, as the diol component, a polycarbonate containing ether diol such as isosorbite as a main component is also included.

Since the injection-molded panel (D) is formed by injection molding, it is possible to take a form having a special shape such as an opening or a curved portion, and to provide an anti-glare effect, for example. Also, fine irregularities can be formed on the image display surface.
Further, as shown in FIG. 5, a display surface portion D1 having fine irregularities for providing an anti-glare effect corresponding to the image display region 1 of the present liquid crystal display device, and a high-class feeling corresponding to the image non-display region 2 are provided. It is also possible to adopt a mode in which a peripheral portion D2 having a smooth surface to be provided is provided on the panel viewing side surface.

  If the arithmetic surface roughness (Ra) of the surface of the display surface portion D1 is 0.1 μm or more, an antiglare effect can be obtained, and if it is 0.7 μm or less, light emitted from the liquid crystal cell is excessively scattered. There is no problem such as blurred image. From this viewpoint, the arithmetic surface roughness (Ra) of the surface of the display surface portion D1 is preferably from 0.1 μm to 0.7 μm, and more preferably from 0.2 μm to 0.5 μm.

The fine irregularities imparting the antiglare property are also useful in improving the visibility of the present invention. In particular, if there is a portion having a rapid phase difference change in the image display area 1 of the injection molded panel (D), a thin boundary line may be recognized, though not so much as to affect the visibility. In such a case, the fine unevenness has an effect of diffusing light emitted from the liquid crystal cell, and thus has an effect of making the boundary line inconspicuous.
The arithmetic surface roughness (Ra) is an arithmetic average roughness defined in JIS B 0601-2013, and is measured by, for example, a surface roughness measuring device, a shape measuring device, a tool microscope, a laser microscope, and other devices. be able to.

On the other hand, the peripheral portion D2 is preferably a smooth surface in order to give a sense of quality, and is particularly preferably a mirror surface showing gloss.
From the above viewpoint, the surface of the peripheral portion D2 preferably has a specular glossiness at an incident / reflection angle of 60 ° based on JIS Z8741 of 85% or more, and more preferably 90% or more.

  Note that the peripheral portion D2 may be formed with a curved peripheral edge or a portion having a different thickness such as a stepped shape or a Taber shape. Further, it is arbitrarily possible to provide an opening such as a through hole, a concave portion, a convex portion, a rib, or the like at an appropriate portion of the peripheral portion D2. Furthermore, various patterns such as a lattice pattern and a staggered pattern can be provided at appropriate places, and printing or the like can be performed on the back surface for decorative purposes.

A coating layer such as a hard coat, an antireflection coat, an antistatic coat, and an antifouling coat may be formed on the surface of the injection molded panel (D), that is, on the viewing side.
Examples of the method for forming the coat layer include a dip coat, a spray coat, and a coat method using an inkjet, a silk screen, a gravure roll, or the like. However, it is not limited to these.
Examples of the coat resin composition include an ultraviolet (UV) curable resin composition, a solvent-curable resin composition, and a thermosetting resin composition. Among them, those having high transparency after the formation of the coat layer are preferable.

The thickness of the injection molded panel (D) varies depending on the intended use, but is preferably about 0.5 mm to 5 mm. When the thickness is 0.5 mm or less, deformation and warping at the time of removal from the mold are liable to occur, and injection molding becomes difficult. On the other hand, when the thickness is 5 mm or more, the thickness of the entire liquid crystal display device becomes too thick, and is not practical.
Therefore, the thickness of the injection-molded panel (D) is preferably 0.5 mm to 5 mm, more preferably 1 mm or more and 3 mm or less, more preferably 1.5 mm or more or 2.5 mm or less.

<Retardation film (E)>
The material and structure of the retardation film (E) are not limited as long as the film has an in-plane retardation (ReE) satisfying the following expression (1).
(1) 3000 nm <ReE ≦ 100000 nm

When a member having a phase difference is arranged between two polarizers having a crossed Nicols relationship and white light is observed, at a certain wavelength, the light is canceled by interference, and at a certain wavelength, the light is transmitted. If the in-plane retardation (ReE) of the retardation film (E) is sufficiently large, transmitted light exists in a large number of wavelength regions, so that an observer can recognize it as white light. On the other hand, those having an in-plane retardation (ReE) exceeding 100,000 nm cannot be applied as a member of a liquid crystal display device because it is extremely difficult to produce a plastic material or the thickness becomes too large.
From this viewpoint, the in-plane retardation (ReE) of the retardation film (E) is greater than 3000 nm and 100000 nm or less, preferably 4000 nm or 50000 nm, and more preferably 5000 nm or 20000 nm. Is more preferred.
The in-plane retardation (ReE) of the retardation film (E) is obtained by measuring in-plane retardations at arbitrary pluralities, for example, five different places in the direction orthogonal to the slow axis direction, and averaging the measured values. Is preferably the in-plane retardation (ReE).

Further, the in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection molded panel (D) in the image display area 1 may have the following relationship (2). preferable. That is, in the above example, the maximum in-plane retardation (ReD) of the display surface portion D1 of the injection molded panel (D) and the maximum in-plane retardation (ReE) of the retardation film (E) are as follows. It is preferable to have the relationship of (2).
(2) ReE-ReD ≧ 3000 nm

The magnitude and direction of the phase difference of the injection molded member may vary depending on the location. For example, in the image non-display area 2, there is an opening at a peripheral portion D2 of the injection molded panel (D), a portion having a different thickness, a non-rectangular portion, or a weld line. In this case, the magnitude and direction of the phase difference may vary greatly. However, even in that case, the difference (ReE) between the in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection-molded panel (D) in the image display area 1. If -ReD) is 3000 nm or more, the effect of improving visibility can be enjoyed.
From this point of view, the difference (ReE-ReD) between the maximum in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection molded panel (D) in the image display area 1. Is preferably 3000 nm or more, more preferably 4000 nm or more, and especially preferably 5000 nm or more. On the other hand, it is assumed that the upper limit value of ReE-ReD is substantially equal to the upper limit value of Expression (1).

The material of the retardation film (E) is not particularly limited. For example, a transparent film having a base resin of one or a mixture of two or more selected from the group consisting of polycarbonate, polyester, polystyrene, polyarylate, polysulfone, polyethersulfone and polyamide can be used. Furthermore, in the case of polycarbonate, polyester, polystyrene, and polyamide, copolymers with different types of monomers are included.
Above all, a film as a base resin selected from the group consisting of polycarbonate, polyester and polyamide is preferable as a material that is transparent, has excellent heat resistance and mechanical properties, and easily produces a phase difference by stretching orientation.

  As the polycarbonate, an aromatic polycarbonate mainly composed of bisphenol A, and as the polyester, polyethylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate and the like can be mentioned as particularly preferred base resins. Further, as the polyamide, a semi-aromatic polyamide such as PA6T or PA9T, which has a relatively high Tg and can maintain transparency even when oriented and crystallized, is particularly suitable.

The retardation film (E) is an oriented film obtained by stretching a substantially non-oriented sheet obtained from the above-described base resin by an appropriate method such as a melt extrusion method or a casting method in a specific direction. Is preferred.
For example, in the case of an oriented polycarbonate film, a polycarbonate is melted, and a non-oriented sheet extruded into a sheet shape is stretched in one direction and, if necessary, in two directions at a temperature equal to or higher than the glass transition temperature. Can be used.
On the other hand, in the case of an oriented polyester film or oriented polyamide film, a resin is melted, and a non-oriented sheet extruded and formed into a sheet is obtained by stretching and heat-treating at least one direction at a temperature equal to or higher than the glass transition temperature. Orientation film can be used.

Examples of a method for adjusting the retardation of the retardation film (E) include a method for adjusting a stretching ratio, a stretching temperature, a film thickness, and the like. However, it is not limited to these.
For example, when the base resin of the retardation film (E) is polyethylene terephthalate, the stretching temperature is preferably from 80 to 130 ° C, and particularly preferably from 85 ° C to 120 ° C. The stretching ratio is preferably from 2.5 to 6.0 times in the case of transverse uniaxial stretching, and more preferably from 3.0 times or more and 5.5 times or less. If the stretching ratio is too high, the resulting film tends to have a mechanical strength, particularly a problem of easily tearing in the stretching direction. On the other hand, if the stretching ratio is too low, the birefringence of the obtained film becomes small, and the retardation becomes small, which is not preferable.

  On the other hand, when the base resin of the retardation film (E) is an aromatic polycarbonate containing bisphenol A as a component, the temperature is preferably from 150 to 180 ° C., particularly preferably from 155 ° C. or more or 170 ° C. or less. The stretching ratio is preferably 3.0 to 5.0 times in the case of longitudinal uniaxial stretching.

  The retardation film (E) has a film surface for the purpose of improving adhesion, water resistance, chemical resistance, and the like with layers formed on the film such as an adhesive layer, a release layer, and an antistatic layer. May be subjected to a surface treatment, that is, a corona discharge treatment or an easy adhesion treatment by a known method.

  The thickness of the retardation film (E) is set such that the ratio of the thickness of the retardation film (E) to the thickness of the injection molded panel (D) is 25 from the viewpoint of suppressing the influence of the retardation of the injection molded panel (D). : 1 to 2: 1, preferably 15: 1 to 2: 1, and more preferably 10: 1 to 2: 1.

Regarding the thickness of the retardation film (E), if it is thin, it is difficult to increase the retardation. Therefore, it is preferable that the retardation film (E) be thick in order to have a high retardation. There is a limit.
From such a viewpoint, the thickness of the retardation film (E) is preferably 25 μm or more and 500 μm or less when the ratio with respect to the thickness of the injection molded panel (D) is within the above range. It is particularly preferable that the thickness be 50 μm or more or 350 μm or less.

  Further, with respect to the thickness of the retardation film (E), depending on the material, depending on the base resin, the intrinsic birefringence differs, the expression state of the retardation varies, and the mechanical strength of the obtained oriented film varies. Preferred thickness is different. For example, when the base resin of the retardation film (E) is polycarbonate, the thickness is preferably 80 μm or more and 500 μm or less, and particularly preferably 100 μm or more or 350 μm or less. On the other hand, when the base resin of the retardation film (E) is polyethylene terephthalate, the thickness is preferably 25 μm or more and 350 μm or less, and particularly preferably 40 μm or more or 250 μm or less.

(Lamination of retardation film (E))
When a member having a phase difference is inserted between orthogonal Nicols and white light is transmitted, when the angle between the absorption axis of the polarizing plate (B) and the slow axis of the member having the phase difference is 45 °, the light is transmitted. Light intensity is maximized. Therefore, in the retardation film (E) of the present invention, the angle between the polarizing plate (B), the slow axis of the retardation film (E), and the absorption axis of the polarizing plate (B) is 45 °. Is most preferable, and in practice, it is preferable to position and arrange so as to be 35 to 55 °. By arranging the retardation film (E) in this manner, even if the positional relationship with the slow axis of the injection molded panel (D) is whatever, the transmitted light intensity sufficient for practical use when wearing sunglasses. Can be secured.
From this viewpoint, the angle is preferably 35 to 55 °, and more preferably 40 ° or more, or 50 ° or less.

  The retardation film (E) includes at least an injection-molded panel (D) (or a laminated panel (F)) and a polarizing plate (B) on the viewer side in order to reduce deformation, displacement, and interfacial reflection. Is preferably fixed to either one of them via a pressure-sensitive adhesive or an adhesive layer. Further, from the viewpoint of preventing interfacial reflection, both the injection molded panel (D) (or the laminated panel (F)) and the polarizing plate (B) on the viewing side are fixed via a transparent adhesive or an adhesive layer. Is more preferred.

  At this time, the pressure-sensitive adhesive or the adhesive composition forming the transparent pressure-sensitive adhesive or the adhesive layer is not particularly limited. It may be a liquid, a gel, or a film. Further, it may have hot-melt properties or may not have hot-melt properties. Further, it may be cross-linked and cured by irradiation with ultraviolet rays or the like.

  Further, when disposing the retardation film (E) on the viewing side of the polarizing plate (B), lamination via a member having a retardation is not preferable for the present invention, but a transparent film having substantially no retardation is used. A member, for example, a transparent member having a maximum in-plane retardation value (Re) of 200 nm or less is laminated on the viewing side of the polarizing plate (B), and a retardation film (E) is laminated via the transparent member. It may be.

<Laminated panel member (F)>
In the present liquid crystal display device, as shown in FIG. 3, instead of the injection molded panel (D) as the front panel, a laminated panel member (F) having the injection molded panel (D) can be used as the front panel. .

  As a configuration of the laminated panel member (F), for example, a member having a configuration in which a functional film is laminated on the viewing side or the back side of the injection molded panel (D) can be exemplified. However, it is not limited to this.

  Examples of the functional film include a substrate film provided with a coating layer such as a hard coat, an antifouling coat, and an antireflection coat, a louver film for preventing peeping, a film having a touch panel sensor layer, and the like. be able to. The functional film can be laminated with the injection molded panel (D) via, for example, an adhesive or an adhesive. However, the method is not limited to the method of laminating via an adhesive or an adhesive.

The functional film may or may not have a retardation. Even if it has a retardation, the in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReF) of the laminated panel member (F) in the image display area are as follows ( If the condition (3) is satisfied, the visibility of the liquid crystal display device can be improved.
(3) ReE-ReF ≧ 3000 nm

  Further, the present invention is preferably applied when the maximum in-plane retardation value (ReF) of the laminated panel member (F) is 350 nm to 5000 nm.

<Explanation of terms>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “preferably larger than X” or “preferably Y” together with “X or more and Y or less” unless otherwise specified. The meaning of "smaller" is also included.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is expressed as “preferably larger than X” or “preferably smaller than Y”. Includes intent.

  Further, in the present specification, the “base resin” means a resin having the largest content among the resins constituting the resin composition, and is usually 50% by mass or more of the resin constituting the resin composition, Among them, the resin is 80% by mass or more, and among them, 90% by mass or more (including 100% by mass). However, when the resin composition contains two types of base resins, the total amount is the above-mentioned mass ratio.

In this specification, the “viewing side” is a side on which display light is emitted from the display screen, and means a side on which a display on the front panel is observed.
The “back side” means the side opposite to the “viewing side”, and means the side on which display light from the display screen enters.
“Transparent” is not limited to colorless and transparent, but includes colored and transparent.

  Hereinafter, the present invention will be described in more detail based on the following Examples and Comparative Examples.

<Preparation of injection molded panel>
Using a polycarbonate (polycarbonate derived from bisphenol A, Tg 145 ° C.) as a molding material, an injection molding machine with a mold clamping pressure of 350 t was used to mold the molding resin at a molding temperature of 280 to 315 ° C. and a mold temperature of 80 ° C. The injection molding panels 1 and 2 (sample D) were prepared by filling the film from the measuring section using a film gate and performing injection molding. At this time, the injection molded panel 1 (sample D1) was manufactured at an injection temperature of 315 ° C., and the injection molded panel 2 (sample D2) was manufactured at an injection temperature of 280 ° C.

  By changing the molding temperature, the injection speed, the pressure-holding conditions, and the like, the developed phase difference was greatly different, but the slow axis direction almost coincided with the resin flow direction. As shown in many documents, it is considered that the contribution by the orientation of molecular chains accompanying the flow of the resin is large.

In this injection molded panel, the flow direction of the resin is almost constant and hardly fluctuates in the direction of the slow axis, and the distance from the gate is the same, except for the end of the molded product due to its shape and gate settings. Then, almost the same phase difference was shown.
Since the thin portion near the gate showed the largest phase difference, the phase difference of the thin portion was defined as the maximum in-plane phase difference (ReD) of the injection molded panel.
The in-plane retardation maximum value (ReD) of the injection molded panel 1 was 1660 nm.
The maximum in-plane retardation value (ReD) of the injection molded panel 2 was 2780 nm.

(Method of measuring phase difference)
The in-plane retardation was measured using a phase difference measuring device KOBRA-WR (manufactured by Oji Scientific Instruments).
The test piece is set in the cutting device, the phase difference measurement software KOBRA-RE is started, and the measurement method is performed with a high phase difference using light having a wavelength of 446.1 nm to 749.2 nm, and the light having a wavelength of 586.4 nm is used. The measured value was defined as the in-plane retardation.

  The in-plane retardation is the refractive index Nx in the slow axis direction (the direction showing the maximum refractive index in the film plane) in the plane of the test piece, and the fast axis direction in the same plane (direction orthogonal to the slow axis direction). Is the value indicated by (Nx−Ny) × d using the refractive index Ny and the film thickness d (nm). Nx-Ny is indicated as a birefringence value Δn.

<Preparation of retardation film>
(Production of polycarbonate retardation film)
Polycarbonate (polycarbonate derived from bisphenol A, Tg 145 ° C.) is melted at 260 ° C., and a sheet having a predetermined thickness obtained by a melt extrusion method is uniaxially stretched at 160 ° C. by a roll stretching method, and the thickness of the original sheet is obtained. And the stretching ratio were adjusted to obtain polycarbonate retardation films 1 and 2 having the following in-plane retardation.
The polycarbonate retardation film 1 (sample E1) had a thickness of 125 μm and an in-plane retardation (ReE) of 3260 nm.
The polycarbonate retardation film 2 (sample E2) had a thickness of 300 μm and an in-plane retardation (ReE) of 5500 nm.

(Production of polyester retardation film)
A mixture obtained by mixing 20 parts by mass of a homopolymer of polyethylene terephthalate and 80 parts by mass of a homopolymer of polyethylene naphthalate was melt-extruded to obtain an unstretched sheet, and then, at 120 ° C., 3.5 times in length and 6.0 in width. The film was biaxially stretched by a factor of 2 to obtain a polyester retardation film 1 (sample E3) having the following in-plane retardation.
The polyester retardation film 1 (biaxially stretched film) had a thickness of 50 μm and an in-plane retardation (ReE) of 4740 nm.

Further, a mixture obtained by mixing 80 parts by mass of a homopolymer of polyethylene terephthalate and 20 parts by mass of a homopolymer of polyethylene naphthalate was melt-extruded, and the unstretched sheet was uniaxially stretched at 90 ° C. by 6.0 times in the transverse direction. A polyester retardation film 2 (sample E4) having the following in-plane retardation was obtained.
The polyester retardation film 2 (uniaxially stretched film) had a thickness of 60 μm and an in-plane retardation (ReE) of 6530 nm.

<Production of liquid crystal display device>
A liquid crystal display is obtained by combining the injection molded panels 1 and 2 (samples D1 and D2) produced as described above with the retardation films 1 and 2 made of polycarbonate or the retardation films 1 and 2 made of polyester (samples E1 to E4). The device.

As shown in FIG. 2, a liquid crystal cell having a backlight light source (C) in which a blue LED and a yellow phosphor are combined, and having a polarizing plate (B) on the viewing side, has an injection-molded panel 1 and 2 on the viewing side. 2 (samples D1 and D2) and a retardation film between the polarizing plate (B) and the injection molded panels 1 and 2 (samples D1 and D2) to obtain a liquid crystal display device.
At this time, a polarizing plate (B) on the viewing side whose absorption axis is inclined by 45 ° from the vertical direction of the screen is used, and a retardation film is used for this, and its slow axis is in the horizontal direction of the liquid crystal display device. It was arranged like. The injection molded panels 1 and 2 (samples D1 and D2) were arranged on the viewing side such that the slow axis was in the vertical direction of the liquid crystal display device. As a result, the angle between the slow axis of the retardation film and the absorption axis of the polarizing plate (B) on the viewing side is 45 °, and the slow axis of the retardation film and the slow axes of the injection molded panels 1 and 2 are different from each other. Was 90 °.
Therefore, it is considered that the retardation film and the injection molded panels 1 and 2 have a relationship of subtraction, and the apparent retardation of these laminated materials is approximately (phase retardation of retardation film−position of injection molded panel). Phase difference).

(Effect judgment method)
The following test was performed using a pseudo white light source obtained by combining a blue LED and a yellow phosphor as the backlight light source (C) and emitting white light.

At the phase difference measurement position near the gate (the position with the highest phase difference), the display state of the image is changed at a position where the polarizing plate regarded as polarized sunglasses has a crossed Nicols relationship with the polarizing plate on the viewing side of the liquid crystal display device. Observed. Furthermore, the angle of the polarizing plate was changed from the relationship of orthogonal Nicols to the relationship of parallel Nicols, and the display state of an image was observed in the same manner.
The determination was made based on the presence or absence of the interference color, the luminance of the screen, and the presence or absence of color change. A combination in which no interference color that is detrimental to the visibility of the image was observed and the luminance did not change significantly even when the angle of the polarizing plate was changed was judged as “○”. Table 1 shows the results of determination in each of the examples and comparative examples.

(Discussion)
Generally, when two retardation films are laminated, the apparent retardation of the laminated film is an additive relationship when the slow axes are in a parallel relationship and a subtractive relationship when the slow axes are in an orthogonal relationship. Become. In the case of neither parallel nor orthogonal, it is said that it can be approximated by a cos curve. Therefore, the minimum value of the apparent phase difference of the laminated film is, as in the liquid crystal device for evaluation described above, the retardation of the two. It can be considered as a subtraction value when the axes are orthogonal.
The injection-molded panel obtained by injection molding has a phase difference of various magnitudes depending on the shape and injection molding conditions, and may have a large variation in the direction of the orientation axis. When considering the characteristics, it is necessary to consider that the positional relationship is in the phase-reduced state (the effective phase difference is minimum). Therefore, it is appropriate to set the lower limit of the phase difference value using the difference between the two as an index.

From this viewpoint, the difference (ReE-ReD) between the maximum in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection molded panel (D) in the image display area is It is considered that the thickness needs to be 3000 nm or more.
Similarly, the difference (ReE-ReF) between the maximum in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReF) of the laminated panel member (F) in the image display area is also 3000 nm. It is considered necessary to be above.
Next, the following test was performed to confirm this validity.

<Discussion confirmation test>
The polycarbonate retardation film 1 (sample E1: thickness 125 μm, in-plane retardation (ReE) 3260 nm) used in the above Examples and Comparative Examples was measured using the absorption axis of the polarizing plate on the viewing side of the liquid crystal display device and the film. Were arranged so that the angle between the slag and the slow axis was 45 °. Next, PET films having a phase difference of 500 nm, 1000 nm, and 1500 nm, respectively, are regarded as front panels instead of the injection-molded panel (D) of the present invention, and are laminated on the viewing side of the phase difference film (E) at various angles. Then, the liquid crystal display device was observed through a polarizing plate having a positional relationship of orthogonal Nicols. The method of determining visibility is the same as in the above-described Examples and Comparative Examples, and the results are shown in the following table.

In Tests 2 to 4 in which the difference in retardation between the retardation film (E) and the front panel was smaller than 3000 nm, it was clearly understood that the visibility deteriorated at an angle of 45 °. On the other hand, in Test 1 in which the difference in retardation between the retardation film (E) and the front panel was 3000 nm or more, it was found that visibility could be improved regardless of the slow axis direction of the front panel.
Thereby, the critical point of the difference between the in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReD) of the injection molded panel (D) in the image display area in the present invention is 3000 nm. Is shown. At the same time, even when a laminated panel member (F) in which a functional film having a retardation is laminated is used as a front panel, the in-plane retardation (ReE) of the retardation film (E) in the image display area is different from the in-plane retardation (ReE). It is shown that the critical point of the difference from the in-plane retardation maximum value (ReF) of the laminated panel member (F) is 3000 nm.
Furthermore, even when the front panel has various orientation angles and directions of phase difference, it has been found that the liquid crystal display device of the present invention can provide an effect of improving visibility.

1 image display area 2 image non-display area (A) liquid crystal cell (B) polarizing plate (C) backlight light source (D) injection molded panel (E) retardation film (F) laminated panel member (G) functional film

Claims (7)

A liquid crystal cell (A), a polarizing plate (B) disposed on the viewing side of the liquid crystal cell (A), and a backlight having a continuous emission spectrum when viewed from the viewing side. And a light source (C).
Injection molded panel (D) is arranged on the viewing side of polarizing plate (B), and retardation film (E) is arranged between polarizing plate (B) and injection molded panel (D),
The retardation film (E) has an in-plane retardation (ReE) satisfying the following expression (1), and the difference between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B). Arranged so that the angle between them is 35-55 °, and
The in-plane retardation maximum value (ReD) of the injection molded panel (D) in the image display area is 350 nm to 5000 nm, and the in-plane retardation (ReE) of the retardation film (E) in the image display area and the injection molded panel ( A liquid crystal display device characterized in that the in-plane phase difference maximum value (ReD) of D) has the following relationship (2).
(1) 3000 nm <ReE ≦ 100000 nm
(2) ReE-ReD ≧ 3000 nm A liquid crystal cell (A), a polarizing plate (B) disposed on the viewing side of the liquid crystal cell (A), and a backlight having a continuous emission spectrum when viewed from the viewing side. And a light source (C).
A laminated panel member (F) having a configuration in which an injection molded panel (D) and a functional film are laminated is arranged on the viewing side of the polarizing plate (B), and the polarizing plate (B) and the laminated panel member are arranged. (F) and a retardation film (E),
The retardation film (E) has an in-plane retardation (ReE) satisfying the following expression (1), and the difference between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B). Arranged so that the angle between them is 35-55 °, and
An in-plane retardation maximum value (ReF) of the laminated panel member (F) in the image display region is 350 nm to 5000 nm;
The in-plane retardation (ReE) of the retardation film (E) and the maximum in-plane retardation (ReF) of the laminated panel member (F) in the image display area have the following relationship (3). Liquid crystal display.
(1) 3000 nm <ReE ≦ 100000 nm
(3) ReE-ReF ≧ 3000 nm The retardation film (E) is formed of a transparent film having a base resin of one or a mixture of two or more selected from the group consisting of polycarbonate, polyester, polystyrene, polyarylate, polysulfone, polyethersulfone, and polyamide. The liquid crystal display device according to claim 1, wherein: The liquid crystal display according to any one of claims 1 to 3 , wherein the resin material constituting the injection molded panel (D) is a kind of resin material selected from the group consisting of polycarbonate, polyester, and acrylic resin. apparatus. And injection molding the panel (D) or laminated panel member (F), and the retardation film (E), according to any of claims 1-4, characterized in that it is laminated with an adhesive or an adhesive Liquid crystal display device. The liquid crystal display device according to any one of claims 1 to 5 , wherein a ratio of a thickness of the retardation film (E) to a thickness of the injection molded panel (D) is 25: 1 to 2: 1. . The injection molded panel (D) is provided with an image display surface having a large number of irregularities on the panel viewing side surface, and the surface of the image display surface has an arithmetic average roughness (Ra) of 0.1 μm to 0.7 μm. the liquid crystal display device according to any one of claims 1 to 6, characterized in that.

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