KR102633523B1 - Liquid Crystal Display Device - Google Patents

Abstract

A liquid crystal display device is provided that has a step between a display screen and the outermost surface, the step is difficult to recognize, and can achieve a bright display. The liquid crystal display device of the present invention includes a liquid crystal cell; a first polarizer disposed on the back side of the liquid crystal cell; a second polarizer disposed on the viewing side of the liquid crystal cell; a cover sheet having an opening at a position corresponding to a display area of a liquid crystal cell disposed on a viewing side of the second polarizer; A third polarizer is disposed on the viewing side of the cover sheet to cover the opening. The opening of the cover sheet is filled with adhesive.

Description

Liquid Crystal Display Device

The present invention relates to liquid crystal display devices.

Liquid crystal displays are used in a wide range of applications, including TVs, smartphones, PC monitors, and digital cameras, and their uses are expanding further. As a result, depending on the purpose of the liquid crystal display device, a form in which the liquid crystal display device is embedded in various structures is adopted. Specific examples of such uses include operation information screens in railway vehicles (e.g., next station guidance for passenger cars), displays such as various instruments and navigation systems installed on the instrument panel or console of automobiles, various instruments in airplane cockpits, hospitals, etc. Examples include monitors installed in security rooms or combat command centers. In this form, a cover sheet having an opening corresponding to the display area of the liquid crystal display device may be placed on the viewing side of the liquid crystal display device as needed for protection of the liquid crystal display device and/or design. In this form, there is no step between the outermost surface of the part containing the liquid crystal display device (e.g., the outermost surface of a case, wall, monitor desk, or cover sheet disposed as necessary) and the display screen. Occurs, and depending on the use and/or situation, the level difference may affect visibility. In order to make it difficult to recognize the level difference, a technique of arranging a photosensitive filter on the viewer's side has been proposed (Patent Document 1). However, with this technology, it is difficult to recognize steps, but there is a problem in that the display screen itself becomes dark.

Patent Document 1: Japanese Patent No. 5877433 Specification

The present invention was made to solve the above conventional problems, and its object is to provide a liquid crystal display device that has a step between the display screen and the outermost surface, the step is difficult to recognize, and can realize a bright display. is to provide.

The liquid crystal display device of the present invention includes a liquid crystal cell; a first polarizer disposed on a back side of the liquid crystal cell; a second polarizer disposed on a viewing side of the liquid crystal cell; a cover sheet having an opening at a position corresponding to a display area of the liquid crystal cell disposed on a viewing side of the second polarizer; A third polarizer is disposed on a viewing side of the cover sheet to cover the opening. The opening of the cover sheet is filled with adhesive.

In one embodiment, the adhesive is a part of the adhesive layer provided between the cover sheet and the third polarizer.

In one embodiment, the adhesive has a refractive index of 1.30 to 1.70.

In one embodiment, the difference between the refractive index of the adhesive and the refractive index of a layer adjacent to the adhesive is 0.2 or less.

According to the present invention, in a liquid crystal display device having a step between a display screen and the outermost surface by a cover sheet having an opening, a polarizer is placed on the visible side of the step, and the opening is filled with an adhesive to form a display screen. Visibility can be improved by making it difficult to recognize steps while maintaining brightness.

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.
Figure 2 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
3 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
Figure 4 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
Figure 5 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
Figure 6 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

A. Overall configuration of liquid crystal display device

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 100 includes a liquid crystal cell 10, a first polarizer 20 disposed on the rear side of the liquid crystal cell 10, and a second polarizer 30 disposed on the viewing side of the liquid crystal cell 10. and a cover sheet 40 disposed on the viewing side of the second polarizer 30 and a third polarizer 60 disposed on the viewing side of the cover sheet 40. The cover sheet 40 has an opening at a position corresponding to the display area of the liquid crystal cell 10. The third polarizer 60 is arranged to cover the opening of the cover sheet 40. According to an embodiment of the present invention, the third polarizer is disposed on the outermost surface side to cover the opening of the cover sheet, thereby making it difficult to recognize the step due to the cover sheet (opening), and as a result, improving the visibility of the liquid crystal display device. can do. More specifically, in addition to making it difficult to recognize the step by flattening the outermost surface by covering the opening of the cover sheet, the step can also be made more difficult to recognize due to the transmittance unique to the polarizer. Additionally, since the polarizer can efficiently transmit polarized light in a predetermined direction, the brightness of the display screen can be maintained compared to a photosensitive filter that reduces the overall light. Below, “making it difficult to recognize a step” is sometimes referred to as “reducing a visual step.”

In the embodiment of the present invention, the opening of the cover sheet 40 is filled with an adhesive. The adhesive may fill only the opening or may be part of the adhesive layer 80 provided between the cover sheet 40 and the third polarizer 60. With this configuration, the air layer formed by the opening is excluded, so reflection and/or refraction at the floor interface can be suppressed. As a result, visual steps can be more significantly reduced while maintaining the brightness of the display screen. The refractive index of the adhesive is preferably 1.30 to 1.70, more preferably 1.40 to 1.60, and still more preferably 1.45 to 1.55. By setting the refractive index of the adhesive in this range, reflection and/or refraction at the floor interface can be further suppressed, and the balance between the brightness of the display screen and visual steps can be more excellent.

In the liquid crystal display device according to the embodiment of the present invention, the absorption axis direction of the second polarizer 30 and the absorption axis direction of the third polarizer 60 may have any appropriate angle depending on the purpose. The absorption axis direction of the second polarizer 30 and the absorption axis direction of the third polarizer 60 are typically substantially perpendicular or parallel, and are preferably substantially parallel. With this configuration, visual steps can be reduced while maintaining the brightness of the display screen. In addition, in the liquid crystal display device according to the embodiment of the present invention, the absorption axis direction of the first polarizer 20 and the absorption axis direction of the second polarizer 30 are substantially perpendicular or parallel, and typically are substantially perpendicular to each other. there is. As used herein, the expressions “substantially orthogonal” and “approximately orthogonal” include cases where the angle formed by the two directions is 90°±10°, preferably 90°±7°, and more preferably 90°±10°. °±5°. The expressions “substantially parallel” and “approximately parallel” include the case where the angle formed by the two directions is 0° ± 10°, preferably 0° ± 7°, and more preferably 0° ± 5°. am. In addition, in this specification, when simply referring to "orthogonal" or "parallel," it may include a substantially orthogonal or substantially parallel state.

The liquid crystal display device according to the embodiment of the present invention may be in so-called O mode or may be in so-called E mode. “O-mode liquid crystal display device” means that the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell and the initial orientation direction of the liquid crystal cell are substantially parallel. “E-mode liquid crystal display device” means that the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell and the initial orientation direction of the liquid crystal cell are substantially orthogonal. “Initial orientation direction of the liquid crystal cell” refers to the direction (i.e., slow axis direction) in which the in-plane refractive index of the liquid crystal layer is maximized as a result of the alignment of the liquid crystal molecules contained in the liquid crystal layer in the absence of an electric field.

Figure 2 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention. In the liquid crystal display device 101, the cover sheet 40 is curved, and the third polarizer 60 is curved along the cover sheet 40. Preferably, the adhesive fills the gap between the cover sheet 40 and the second polarizer 30 that occurs when the cover sheet 40 is curved. The cover sheet 40 may be curved into any suitable shape. Specifically, the poet's side may be curved to be convex, or the poet's side may be curved to be concave. Additionally, the cover sheet 40 may be curved with any direction within its surface as an axis. In addition, like the liquid crystal display device 102 shown in FIG. 3, the liquid crystal cell 10, the first polarizer 20, and the second polarizer 30 may be curved along the cover sheet 40. The liquid crystal display devices 101 and 102 of this embodiment, which have curved cover sheets, have a wide range of design options and have great commercial value.

Figure 4 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention. The liquid crystal display device 103 includes a liquid crystal cell 10A, a first polarizer 20A disposed on the rear side of the liquid crystal cell 10A, and a second polarizer 30A disposed on the viewing side of the liquid crystal cell 10A. and a liquid crystal cell 10B, a first polarizer 20B disposed on the back side of the liquid crystal cell 10B, a second polarizer 30B disposed on the viewing side of the liquid crystal cell 10B, and a second polarizer. It is provided with a cover sheet 40 disposed on the viewing side of 30A and 30B, and a third polarizer 60 disposed on the viewing side of the cover sheet 40. The cover sheet 40 of the liquid crystal display device 103 has a first transparent portion 42A at a position corresponding to the display area of the liquid crystal cell 10A, and a first transparent portion 42A is provided at a position corresponding to the display area of the liquid crystal cell 10B. 2 It is provided with a transparent portion (42B). The liquid crystal display device 103 has two display screens corresponding to each liquid crystal cell, and the third polarizer is disposed on the outermost surface side so as to cover the two transparent portions of the cover sheet, so that the outermost surface of the device and the two display screens By making it difficult to recognize the difference between the two display screens, visibility on the two display screens can be improved. In addition, although a liquid crystal display device having two display screens and two corresponding liquid crystal cells has been described as an example, the liquid crystal display device of the present invention may have three or more display screens and corresponding liquid crystal cells.

Figure 5 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention. The liquid crystal display device 104 of this embodiment has two display screens, similar to the liquid crystal display device 103. Additionally, in this embodiment, the cover sheet 40 is bent at the bent portion 90 between the transparent portion 42A and the transparent portion 42B, and the third polarizer 60 is bent along the cover sheet 40. there is. Accordingly, the liquid crystal display device 104 can display images in different directions using two display screens. In addition, the liquid crystal display device of the present invention may have a cover sheet having a plurality of bent portions, and three or more display screens and corresponding liquid crystal cells with each bent portion interposed therebetween.

The liquid crystal display device according to the embodiment of the present invention can be used, for example, by being included in (typically embedded in) various structures. Specific examples of structures include architectural structures (e.g., walls of guard rooms or combat command posts), railway vehicles (e.g., walls above doors), automobiles (e.g., instrument panels, consoles), airplanes (e.g., cockpits), home appliances, and AV equipment. You can.

In practical terms, the liquid crystal display device according to the embodiment of the present invention additionally includes a backlight unit (not shown). The backlight unit typically includes a light source and a light guide plate. The backlight unit may further include any suitable other members (eg, diffusion sheet, prism sheet).

The liquid crystal display device according to the embodiment of the present invention may further include any other suitable members. For example, a so-called λ/4 plate is disposed between the second polarizer 30 and the cover sheet 40 and/or between the cover sheet 40 (actually the adhesive layer 80) and the third polarizer 60. It can be done. With this configuration, the visual step can be further reduced. Additionally, the λ/4 plate may be replaced with a laminate of a λ/4 plate and a λ/2 plate. Additionally, for example, an optical compensation layer (retardation film) different from the λ/4 plate may be additionally disposed. The optical properties, number, combination, arrangement position, etc. of different optical compensation layers may be appropriately selected depending on the purpose and desired optical properties. Additionally, for example, various surface treatment layers may be disposed on the outermost surface. Specific examples of the surface treatment layer include an anti-glare layer, an anti-reflection layer, and a hard coat layer. A plurality of surface treatment layers may be disposed. The type, number, and combination of surface treatment layers may be appropriately selected depending on the purpose.

The above embodiments may be appropriately combined, and the configuration in the above embodiment may be replaced with an optically identical configuration. For example, as shown in FIG. 6, the embodiment of FIG. 3 and the embodiment of FIG. 4 may be combined. Specifically, FIG. 6 shows that the liquid crystal display device 105 includes a liquid crystal cell 10A and a liquid crystal cell 10B, each of which is curved, and the cover sheet 40 is positioned in the display area of the liquid crystal cell 10A. A first transparent portion 42A is provided at a corresponding position, and a second transparent portion 42B is provided at a position corresponding to the display area of the liquid crystal cell 10B. For matters not described in this specification, the configuration of a liquid crystal display device that is well-known and common in the art may be adopted.

Hereinafter, each member and optical film constituting the liquid crystal display device will be described.

B. Liquid crystal cell

The liquid crystal cell 10 has a pair of substrates 11 and 11' and a liquid crystal layer 12 as a display medium sandwiched between the substrates. In a general configuration, a color filter and a black matrix are provided on one substrate, and a switching element that controls the electro-optical characteristics of the liquid crystal is provided on the other substrate, and a scanning line and source signal that provide a gate signal to this switching element are provided. A signal line, a pixel electrode, and a counter electrode are provided. The gap (cell gap) of the substrate is controlled by a spacer or the like. For example, an alignment film made of polyimide can be installed on the side of the substrate in contact with the liquid crystal layer.

In one embodiment, the liquid crystal layer includes liquid crystal molecules aligned in a homeotropic arrangement in the absence of an electric field. “Liquid crystal molecules aligned in a homeotropic arrangement” refers to a state in which the orientation vector of the liquid crystal molecules is aligned perpendicular to the plane of the substrate as a result of the interaction between the liquid crystal molecules and the aligned substrate. Such a liquid crystal layer (and, as a result, a liquid crystal cell) typically exhibits a three-dimensional refractive index of nz>nx=ny. A representative example of a drive mode using a liquid crystal layer exhibiting such a three-dimensional refractive index is vertical alignment (VA) mode. VA mode includes multi-domain VA (MVA) mode.

In another embodiment, the liquid crystal layer includes liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field. “Liquid crystal molecules aligned in a homogeneous arrangement” refers to a state in which the orientation vector of the liquid crystal molecules is aligned parallel and uniformly with respect to the plane of the substrate as a result of the interaction between the aligned substrate and the liquid crystal molecules. Such a liquid crystal layer (and, as a result, a liquid crystal cell) typically exhibits a three-dimensional refractive index of nx>ny=nz. Representative examples of driving modes using a liquid crystal layer exhibiting such a three-dimensional refractive index include in-plane switching (IPS) mode and fringe field switching (FFS) mode. In addition, the above IPS mode includes a super-in-plane switching (S-IPS) mode or an advanced-super-in-plane switching (AS-IPS) mode employing V-shaped electrodes or zigzag electrodes. Additionally, the FFS mode includes an advanced-fringe field switching (A-FFS) mode or an ultra-fringe field switching (U-FFS) mode employing V-shaped electrodes or zigzag electrodes.

C. Polarizer

Any suitable polarizer can be employed as the first polarizer, second polarizer, and third polarizer (hereinafter sometimes collectively referred to simply as polarizer). For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films containing iodine or dichroic dyes. Examples include those that have been dyed and stretched with a dichroic substance, and polyene-based oriented films such as dehydrated PVA products and dechlorinated polyvinyl chloride products. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxial stretching is used because it has excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Additionally, it may be dyed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can contamination and anti-blocking agents on the surface of the PVA-based film be washed away, but also the PVA-based film can be expanded to prevent dyeing stains.

The thickness of the polarizer is preferably 1 μm to 80 μm, more preferably 10 μm to 50 μm, further preferably 15 μm to 40 μm, and particularly preferably 20 μm to 30 μm. If the thickness of the polarizer is within this range, it can have excellent durability under high temperature and high humidity.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 40.0% to 46.0%, more preferably 41.0% to 44.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

The first polarizer 20, the second polarizer 30, and the third polarizer 60 may each have a protective layer (not shown) provided on at least one side. That is, the first polarizer 20, the second polarizer 30, and the third polarizer 60 may each be included in the liquid crystal display device as polarizing plates.

The protective layer is formed from any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that become the main component of the film include cellulose resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. Transparent resins such as phone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based resins can be mentioned. Additionally, thermosetting resins or ultraviolet curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, silicone, etc. are also included. In addition, for example, glassy polymers such as siloxane polymers can also be mentioned. Additionally, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01/37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, isobutene and N- A resin composition containing an alternating copolymer made of methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film may be, for example, an extrusion molded product of the resin composition.

The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and still more preferably 5 μm to 150 μm. In addition, when surface treatment is applied, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.

When a protective layer (hereinafter referred to as an inner protective layer) is installed on the liquid crystal cell side of the first polarizer 20, the second polarizer 30, and/or the third polarizer 60, the inner protective layer is optically It is preferable that it is isotropic. “Optically isotropic” means that the in-plane phase difference Re(550) is 0 nm to 10 nm and the thickness direction phase difference Rth(550) is -10 nm to +10 nm. The inner protective layer may be composed of any suitable material as long as it is optically isotropic. The material may be suitably selected, for example, from the materials described above for the protective layer.

The thickness of the inner protective layer is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 15 μm to 95 μm.

D. Cover sheet

Typically, when a liquid crystal display device is included in a structure and used, the cover sheet 40 may be installed to protect the liquid crystal display device and/or as requested by design. Therefore, the cover sheet 40 typically has an opening corresponding to the display area of the liquid crystal cell so as not to interfere with the display function of the liquid crystal display device.

The cover sheet may be comprised of any suitable material. Representative examples of constituent materials include resin. This is because it has appropriate strength as a cover sheet and is easy to mold into a desired shape and form an opening. Specific examples of resin include polyarylate, polyamide, polyimide, polyester, polyaryl ether ketone, polyamidoimide, polyester imide, polyvinyl alcohol, polyfumaric acid ester, polyether sulfone, polysulfone, norbornene resin, poly Carbonate resin, cellulose resin, and polyurethane can be mentioned. These resins may be used individually or in combination.

In one embodiment, the cover sheet has light blocking properties. Light-shielding properties can be imparted by blending a light-shielding material (e.g., carbon black) into the resin when molding the cover sheet.

The thickness of the cover sheet is preferably 0.1 mm to 5 mm, and more preferably 0.3 mm to 3 mm. With this thickness, appropriate strength can be achieved as a protective member of a liquid crystal display device. According to the present invention, as described above, physical steps that may occur due to the thickness of the cover sheet can be eliminated and visual steps can be significantly reduced.

E. Adhesive layer

In the embodiment of the present invention, the opening of the cover sheet 40 is filled with an adhesive as described above. As a result, the air layer formed by the opening is excluded, so reflection and/or refraction at the floor interface can be suppressed. As a result, visual steps can be more significantly reduced while maintaining the brightness of the display screen.

As described above, the refractive index of the adhesive is preferably 1.30 to 1.70, more preferably 1.40 to 1.60, and still more preferably 1.45 to 1.55. By setting the refractive index of the adhesive in this range, reflection and/or refraction at the floor interface can be further suppressed, and the balance between the brightness of the display screen and the visual step can be more excellent.

The difference between the refractive index of the adhesive and the refractive index of the layer adjacent to the adhesive is preferably 0.20 or less, and more preferably 0 to 0.15. By setting the difference between the refractive index of the adhesive and the refractive index of the adjacent layer within this range, the above effect can be further promoted when the refractive index of the adhesive is within a predetermined range.

As described above, the adhesive may fill only the opening or may be part of the adhesive layer 80 provided between the cover sheet 40 and the third polarizer 60. In the latter case, the thickness of the adhesive layer (thickness other than the portion corresponding to the opening of the cover sheet) can be appropriately set depending on the purpose, adhesive strength, etc. The thickness of the adhesive layer is preferably 1 μm to 500 μm, more preferably 1 μm to 200 μm, and still more preferably 1 μm to 100 μm.

The adhesive layer may be composed of any suitable adhesive having the above properties. Specific examples include adhesives whose base polymers include acrylic polymers, silicone polymers, polyester, polyurethane, polyamide, polyether, fluorine-based polymers, and rubber-based polymers. Preferably, it is an adhesive that uses an acrylic polymer as a base polymer (acrylic adhesive). This is because it has excellent optical transparency, appropriate adhesive properties (wetting, cohesiveness, and adhesiveness), and excellent weather resistance and heat resistance.

[Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Additionally, the measurement method for each characteristic is as follows.

(1) Physical step

The presence or absence of irregularities on the surface on the viewing side of the liquid crystal display devices obtained in the examples and comparative examples was confirmed.

(2) Visual step

The level difference was visually confirmed while images were actually displayed on the liquid crystal display devices obtained in Examples and Comparative Examples. It was evaluated based on the following criteria.

A: Step differences are practically not recognized, and there is no problem at all in visualizing the image.

B: The level difference is recognized, but has no substantial effect on the visibility of the image.

C: A level difference that causes a sense of discomfort is recognized when viewing the image.

D: A level difference that significantly affects the visibility of the image is clearly recognized.

(3) Brightness of the display screen

The luminance of the liquid crystal display devices obtained in Examples and Comparative Examples when the entire screen was displayed in white was measured. The luminance ratio when the luminance of Comparative Example 1 was set to 100% was used to evaluate the results according to the following criteria.

A: Brightness ratio exceeds 90%

B: Brightness ratio 80% to 90%

C: Brightness ratio 70% to 80%

D: Luminance ratio less than 70%

[Example 1]

(i) Polarizer

Three commercially available polarizers (manufactured by Nitto Denko, product name "CWQ1463VCUHC") were prepared and used as a first polarizer (polarizer), a second polarizer (polarizer), and a third polarizer (polarizer).

(ii) Cover sheet

A commercially available methacrylic resin sheet (manufactured by Nitto Resin Industries, product name "Flat N-885", thickness 1.0 mm) was used to create an opening through a portion corresponding to the display area of the liquid crystal cell described later.

(iii) liquid crystal cell

The liquid crystal panel was taken out from the product name "plus one" (IPS mode) manufactured by Century, and the optical film affixed to the top and bottom of the liquid crystal cell was further removed and the surface from which the optical film was removed was cleaned. The liquid crystal cell obtained in this way was used.

(iv) Fabrication of liquid crystal display devices

The polarizing plate (i) (second polarizer) above, the cover sheet (ii) above, and the polarizing plate (third polarizer) above (i) were bonded to one side of the liquid crystal cell in this order from the liquid crystal cell side. The cover sheet was bonded so that the opening corresponded to the display area of the liquid crystal cell. The third polarizer and the cover sheet were bonded together with an adhesive (manufactured by Nitto Denko, product name "CS99110", thickness 250 μm, storage modulus G' = 120 KPa), and the openings of the cover sheet were filled with the adhesive. In this example, four layers of this adhesive were overlapped to fill the opening. Additionally, the above-mentioned polarizing plate (i) (first polarizer) was bonded to the other side of the liquid crystal cell. Here, each optical film was bonded so that the absorption axis of the first polarizer and the absorption axis of the second polarizer were orthogonal, and the absorption axis of the second polarizer and the absorption axis of the third polarizer were parallel. Additionally, a liquid crystal display device was manufactured by including the backlight unit taken out from “plus one” in (iii) above on the outside of the first polarizer. The obtained liquid crystal display device was subjected to the evaluation of (1) to (3) above. The results are shown in Table 1.

[Comparative Example 1]

A liquid crystal display device was manufactured in the same manner as in Example 1 except that the third polarizer was not provided, that is, the cover sheet was used as the outermost layer. The obtained liquid crystal display device was subjected to the same evaluation as Example 1. The results are shown in Table 1.

[Comparative Example 2]

A liquid crystal display device was produced in the same manner as in Example 1, except that a commercially available photosensitive filter (manufactured by Fujifilm, product name "Neutral Density Filter ND-0.2", transmittance 64%) was attached in place of the third polarizer. The obtained liquid crystal display device was subjected to the same evaluation as Example 1. The results are shown in Table 1.

[Comparative Example 3]

A liquid crystal display device was manufactured in the same manner as in Example 1 except that the third polarizer and the cover sheet were bonded together with a normal acrylic adhesive, and the openings of the cover sheet were not filled. The obtained liquid crystal display device was subjected to the same evaluation as Example 1. The results are shown in Table 1.

composition of the poet's side physical step visual step brightness Example 1 Third polarizer/cover sheet (with opening filling) radish A A(90)
Comparative Example 1 cover sheet you D A(100) Comparative example 2 Photosensitive filter/cover sheet radish C D(64) Comparative example 3 Third polarizer/cover sheet (no opening filling) radish C C(79)

The brightness in parentheses is the brightness ratio (%) when the brightness of Comparative Example 1 is set to 100%.

As is clear from Table 1, the physical step was eliminated in the liquid crystal display device of the embodiment of the present invention, and the balance between the visual step and the brightness of the display screen was excellent. The liquid crystal display device of Comparative Example 1, which used the cover sheet as the outermost layer on the viewing side, had a bright display screen, but the physical steps were not resolved and the visual steps were poor enough to affect visibility. In the liquid crystal display device of Comparative Example 2 using a photosensitive filter, the physical step was eliminated, but both the brightness of the display screen and the visual step were poor. The brightness of the liquid crystal display device of Comparative Example 3, in which the opening of the cover sheet was not filled, was improved compared to Comparative Example 2, but the visual step was poor.

The liquid crystal display device of the present invention is used in portable devices such as portable digital assistants (PDAs), mobile phones, watches, digital cameras, and portable game consoles, OA devices such as computer monitors, laptops, and copiers, video cameras, liquid crystal TVs, microwave ovens, and AV devices. Household electrical equipment such as equipment, back monitors, car navigation system monitors, automotive equipment such as car audio, display equipment such as information monitors for commercial stores, security equipment such as surveillance monitors, nursing monitors, medical monitors, etc. It can be used for various purposes such as nursing and medical equipment. In particular, the liquid crystal display device of the present invention can be preferably used in a form embedded in a structure.

10: liquid crystal cell
20: first polarizer
30: second polarizer
40: cover sheet
60: third polarizer
80: Adhesive layer
100: liquid crystal display device

Claims (4)

a liquid crystal cell,
A first polarizer disposed on the back side of the liquid crystal cell,
a second polarizer disposed on a viewing side of the liquid crystal cell;
a cover sheet having an opening at a position corresponding to a display area of the liquid crystal cell disposed on a viewing side of the second polarizer;
A third polarizer is disposed on a viewing side of the cover sheet to cover the opening,
The opening of the cover sheet is filled with adhesive,
The cover sheet is composed of a resin sheet with a thickness of 0.3 mm to 3 mm,
wherein the cover sheet is a single layer,
Liquid crystal display device. According to claim 1,
A liquid crystal display device, wherein the adhesive is a part of an adhesive layer provided between the cover sheet and the third polarizer. According to claim 1,
A liquid crystal display device wherein the adhesive has a refractive index of 1.30 to 1.70. The method of claim 1 or 2,
A liquid crystal display device wherein the difference between the refractive index of the adhesive and the refractive index of a layer adjacent to the adhesive is 0.2 or less.