WO2002067044A1

WO2002067044A1 - Liquid crystal display employing plastic substrate

Info

Publication number: WO2002067044A1
Application number: PCT/JP2002/001208
Authority: WO
Inventors: Hideaki Yamashita; Takeshi Fujiyama
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2001-02-19
Filing date: 2002-02-13
Publication date: 2002-08-29
Also published as: TW575765B; JPWO2002067044A1

Abstract

A liquid crystal display (1) comprising a liquid crystal display section (11) for displaying an image by a liquid crystal (11a) clamped by two sheets of plastic substrates (11b) having a pair of electrodes, and an upper member (2) selected from a display cover for protecting the liquid crystal display (1) against external force and a front light guide plate. The liquid crystal display (1) employs the plastic substrates (11b) where the liquid crystal display section (11) and the upper member (2) are laid tightly through an adhesive layer (3).

Description

Description Liquid crystal display device using plastic substrate

Technical field

The present invention relates to a liquid crystal display device used for a portable information terminal, a mobile phone, and the like, and particularly to a liquid crystal display device using a plastic substrate.

Background art

Many liquid crystal display devices are being commercialized as flat panel displays along with cathode ray tubes and plasma displays, and it is expected that their size and definition will continue to increase in the future. On the other hand, in the field of mobile communication systems such as mobile information terminals and mobile phones, it is well known that the market for liquid crystal display devices has been expanding at a tremendous rate in recent years. Most liquid crystal display devices generally use a glass substrate with a thickness of about 0.7 mm, but with the growing market needs in the field of mobile communication systems for higher definition, thinner and lighter displays. However, its thickness is rapidly decreasing, and at present it is around 0.4 mm.

Glass substrates are usually manufactured by molding and polishing, but the need for thinner walls mentioned above raises the problem of increasing manufacturing costs. Glass has a weak impact resistance, and has the disadvantage that the display is cracked and damaged by the impact of manufacturing glass substrates, assembling liquid crystal display devices, handling in the market or dropping. For this reason, the structure and arrangement around the liquid crystal display panel in terminals such as mobile phones, which are final products, have been devised to absorb impact.

FIG. 7 shows the structure of a conventional liquid crystal display device using a glass substrate. Figure 7 The liquid crystal display device shown includes a liquid crystal cell 11 in which a liquid crystal 11 a is sandwiched between two glass substrates 20 each having a pair of electrodes (not shown), and an adhesive layer 1 above and below the liquid crystal cell 11. 4 is provided with a liquid crystal display panel 1 comprising a polarization / phase plate 12 and a semi-transmissive reflection plate 13 provided through the intermediary of the liquid crystal display panel 1 to protect the liquid crystal display panel 1 from external force. An upper member selected from a transparent display cover or a front light guide plate 2 formed of glass, polycarbonate, acrylic resin or the like and having excellent mechanical strength is provided, and a cushion such as a sponge is provided at a lower portion. A cushioning material 21 that plays a role is arranged. In addition, an air layer 22 is formed between the display cover or the light guide plate 2 for front light (hereinafter abbreviated as display cover 2) and the liquid crystal display panel 1 to form an air gap 22 having a constant thickness. Generally, even if the display cover or the like 2 is pushed by a force, the force is not transmitted to the liquid crystal display panel 1. For example, although not shown in a cellular phone or the like, a display cover or the like 2 is attached to an outer surface of a housing (outer material) of the telephone, and a liquid crystal cell In general, an air space 22 is provided for 11 in such a manner as to be incorporated into the housing (outer material) of the telephone.

In the above, the “light guide plate for front light” is a light guide plate provided on the upper surface of the liquid crystal display panel, and is a light guide plate for a liquid crystal display device provided with a front light such as a light emitting diode (LED) light source. This is a light guide plate for uniformly diffusing light to the upper surface of the liquid crystal display panel. In some cases, a lower member (not shown) selected from (c) a light guide plate for a pack light or (d) a holder for fixing a panel is provided below the liquid crystal display panel. Here, the light guide plate for the backlight is a light guide plate provided on the lower surface of the liquid crystal display panel. The light guide plate for the liquid crystal display device is provided with a backlight such as a light emitting diode (LED) light source. Is a light guide plate for uniformly diffusing the light to the lower surface of the liquid crystal display panel. The panel fixing holder is a holder provided on the lower surface of the liquid crystal display panel for fixing the liquid crystal display panel. Usually as a top member

(a) When a display cover is used to protect the liquid crystal display from external force, (c) a light guide plate for a backlight is used as the lower member, and (b) a front light guide plate is used as the upper member. When a light guide plate for light is used, (d) a panel fixing holder is used as the lower member.

In such a liquid crystal display device, since the air layer 22 is provided between the liquid crystal display panel 1 and the display cover 2 or the like, the display by the liquid crystal display panel 1 looks slightly deep. In addition, in the conventional liquid crystal display device, in order to achieve a clear display, an anti-reflection film is formed to prevent reflection caused by a refractive index difference between the polarization / phase plate 12, the display cover 2, and the air layer 22. It is not uncommon for expensive and special coatings such as 23, etc., and light scattering functions to be added to the adhesive layer 14 such as the polarization / phase plate 12 and the semi-transmissive reflector 13. On the other hand, the development of displays using plastic substrates that are lighter, have better mechanical strength, and can be made thinner at low cost as well as technically easy as a raw material is also in progress. Handy terminals, mobile phones, watches, etc. Has already been commercialized. Liquid crystal display devices using plastic substrates (0.1 mm to 0.4 mm thick) have superior mechanical properties such as "not cracked" or "not chipped" during normal use compared to glass substrates. While having strength, it is possible to make the display itself thinner and lighter. Therefore, it is thought that it will further help to keep the size, weight and thickness of mobile phones and personal digital assistants, which are expected to become more sophisticated in the future, at the current level. In addition to flat display devices such as flat panel displays, wearable devices that fit to the human body, such as curved display devices, are designed from the viewpoint of design. Also attracting attention for use.

The advantages of using a plastic substrate are not limited to these, and there are also quality advantages. For example, one of the advantages is that "low-temperature bubbles", which is a problem in a liquid crystal display device using a glass substrate, are not generated. This is because the linear expansion coefficient of the liquid crystal material differs from that of the glass material by one digit. Air bubbles are created by insolubilizing dissolved gas components and collecting the generated gas. This phenomenon is also a blast that is equivalent to the damage to the display described above, and subsequent display display is impossible. In other words, in assembling a liquid crystal display device using a glass substrate, the selection of the liquid crystal material, its injection amount, and the material of the peripheral part is limited. In contrast, the above-described phenomenon does not occur in the case of using a plastic substrate because the substrate has a linear expansion coefficient substantially equal to that of the liquid crystal material.

However, the industrialization of liquid crystal display devices using plastic substrates has only just begun in mobile phones and other portable information device terminals, and the composition of final products using these substrates is not limited to conventional glass. At present, the same configuration as that of the liquid crystal display device using the substrate is applied as it is. That is, since the plastic substrate is relatively thin compared to the glass substrate, the parallax in the liquid crystal display (that is, if the liquid crystal layer and the reflection plate exist through the thick substrate, the image display of characters and the like appears double. The appearance of shadows on the outer shape of characters is small, and only some measures are taken for cost advantage, such as installing a transflective reflector outside the liquid crystal cell. .

Another major problem with liquid crystal displays using plastic substrates is the "pressing bubble problem". This is an iron ball (diameter 11 mm) on the LCD panel It has been evaluated by a drop test. Plastic materials, unlike glass, have a large gas (or water vapor) permeability coefficient, so that the gas (or moisture) in the atmosphere diffuses and dissolves in the liquid crystal cell until it reaches a saturated state at a certain temperature and pressure. . For this reason, plastic materials (polycarbonate, polyethersulfone, polyarylate, polyester or alicyclic resin) that are generally used as substrates for liquid crystal cells are provided with a layer of inorganic gas barrier, but not as large as glass. At present, the gas permeability coefficient has not been realized, and it is inevitable that the permeated gas and moisture reach a saturated state faster than when a glass substrate is used. Therefore, when the volume occupied by the liquid crystal relative to the volume of the liquid crystal cell is smaller than in the initial state of manufacture and the stiffness of the substrate material is small, the negative pressure state is maintained while the plastic substrate is bent inside the liquid crystal cell due to the surface tension of the liquid crystal As a result, the gas diffusion rate will increase.

That is, when the liquid crystal material is close to the saturated state of the gas due to gas diffusion, the substrate of the liquid crystal display device is deformed by local external force, and the liquid crystal in the pressing portion is eliminated, so that the cell gap is instantaneously changed. When the pressure decreases, the liquid crystal cell volume instantaneously becomes smaller than the liquid crystal occupied volume, and the internal pressure rises. The increased pressure and the elasticity of the spacers and the substrate present in the liquid crystal cell cause a reaction in which the liquid crystal cell volume tends to return to its original state. Due to the so-called "cavitation phenomenon", decompressed air bubbles are generated in the liquid crystal cell, and subsequently, as in the case of low-temperature air bubbles, the insolubilization of dissolved gas components is promoted. Air bubbles are generated. As with the expansion and contraction due to heat, a typical external force basically induces bubble generation, whether it is a force that pushes the substrate or a force that pulls it, as long as it changes the “cell volume / liquid crystal occupied volume ratio”. This leads to the destruction of the liquid crystal display device. To prevent the cell gap from changing locally even when subjected to an external force, the elastic modulus of the plastic substrate material should be close to the glassy state, the thickness of the substrate should be increased many times that of glass, or the inside of the liquid crystal cell should be changed. In order to improve the stiffness (rigidity) of the substrate, it is conceivable to increase the number of spacers existing in the image as much as possible for image display. However, the adoption of such means not only reduces the flexibility inherent in plastic substrate materials, but also increases the contrast ratio of liquid crystal display devices that use glass substrates, and provides bright, clear, and low-parallax liquid crystals. It is difficult to realize display, and it is not possible to achieve a liquid crystal display device that is thin and has excellent durability against external force. Therefore, the present invention pays attention to the configuration at the final product (set) stage in which the liquid crystal display device is incorporated, and the liquid crystal display device using a conventional plastic substrate which is not different from the configuration using a glass substrate at all. It was found that the problem of pressurized air bubbles could be easily solved by using a unique configuration for the above.

That is, the present invention realizes a liquid crystal display that has a high contrast ratio, is bright, clear, and has little parallax while maintaining the advantages of a liquid crystal display device using a plastic substrate, without generating bubbles in the liquid crystal cell, and is resistant to external force. It is an object of the present invention to provide a liquid crystal display device using a plastic substrate having excellent properties. Summary of the Invention

A liquid crystal display device using a plastic substrate according to the present invention includes a liquid crystal display portion that performs display using liquid crystal sandwiched between two plastic substrates provided with a pair of electrodes, and a liquid crystal display portion provided above the liquid crystal display portion. a) Display cover to protect the LCD display from external force or (b) Front light A liquid crystal display device comprising an upper member selected from a light plate, wherein the liquid crystal display unit and the (a) display cover or (b) an upper member selected from a light guide plate for a front light are adhered through an adhesive layer. This is a liquid crystal display device using a plastic substrate.

According to the present invention, a liquid crystal display device using a plastic substrate having a high contrast ratio, a bright, clear, and low parallax liquid crystal display, and having a thin and excellent durability against an external force can be realized as when an iron ball is dropped. A liquid crystal display using a plastic substrate that does not generate bubbles in the liquid crystal cell of the liquid crystal display by converting the external force of a local point load into a surface load that can be received by the entire liquid crystal display with an adhesive layer The device can be realized. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing a structure of a liquid crystal display device using a plastic substrate according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of a liquid crystal display device using a plastic substrate according to another embodiment II of the present invention.

FIG. 3 is a perspective view showing one embodiment of the adhesive layer 3 used in the present invention. FIG. 4 is a perspective view showing another embodiment of the adhesive layer 3 used in the present invention.

FIG. 5 is a perspective view showing still another embodiment of the adhesive layer 3 used in the present invention.

FIG. 6 is a perspective view showing still another embodiment of the adhesive layer 3 used in the present invention.

FIG. 7 is a cross-sectional view showing a structure of a conventional liquid crystal display device using a glass substrate. Detailed Disclosure of the Invention

According to the present invention, there is provided a liquid crystal display section for displaying by a liquid crystal sandwiched between two plastic substrates provided with a pair of electrodes, and (a) a liquid crystal display section provided above the liquid crystal display section from an external force. A liquid crystal display device comprising a display cover for protection or (b) an upper member selected from a light guide plate for a front light, wherein the liquid crystal display portion and the display cover (a) or (b) a front light A liquid crystal display device using a plastic substrate, in which an upper member selected from a light guide plate is closely arranged via an adhesive layer, and has a local point load, such as when an iron ball is dropped. By converting the external force into a surface load that can be received by the entire liquid crystal display unit using an adhesive layer, the cell gap is not locally changed even when external force is applied, thereby suppressing the generation of bubbles in the liquid crystal cell. so Wear. In addition, the adhesive layer can be made considerably thinner than the air space, so that it can be made even thinner, and the liquid crystal display can be seen a little deeper.

In the liquid crystal display device using the plastic substrate of the present invention, a lower member selected from (c) a light guide plate for backlight or (d) a holder for fixing a panel is further provided below the liquid crystal display portion. The liquid crystal display unit and the lower member selected from (c) the light guide plate for pack light or (d) one of the panel fixing holders may be arranged in close contact with an adhesive layer therebetween. By adopting such an aspect, an external force of a local point load, such as when an iron ball is dropped, is converted into a surface load that can be received by the entire liquid crystal display unit by the adhesive layer, and the lower member is similarly formed. Since the liquid crystal cell is further provided with an adhesive layer interposed therebetween, the liquid crystal cell can also exert a reinforcing effect on the entire liquid crystal display portion, and can sufficiently exhibit the function of not locally changing the cell gap even under the above-mentioned external force. This is preferable because the generation of bubbles in the interior can be suppressed.

In the case of the above structure, an upper portion provided above the liquid crystal display portion The material may be (a) a display cover for protecting the liquid crystal display from external force, and the lower member provided below the liquid crystal display may be a combination of (c) a light guide plate for a pack light. A light guide plate for brightening the liquid crystal display section is provided, and light from a pack light for the liquid crystal display panel provided with a backlight such as a light emitting diode (LED) light source is provided below the liquid crystal display panel. It is preferable because it can be uniformly diffused to the side surface.

The upper member provided above the liquid crystal display section is (b) a light guide plate for front light, and the lower member provided below the liquid crystal display section is (d) a holder for fixing the panel. Is also preferable. Also in this case, the light guide plate is provided to make the image on the liquid crystal display portion bright and easy to see, and the light guide plate for the front light also serves as the display cover (a), and the light source of the light emitting diode (LED) This is preferable because light from a front light for a liquid crystal display panel provided with a front light can be uniformly diffused to the upper surface of the liquid crystal display panel. Further, in the liquid crystal display device using the plastic substrate of the present invention, the adhesive layer is an adhesive layer having an antireflection function, which is a multilayered resin layer composed of at least two types of resins having different refractive indexes. It is preferable. By adopting such an embodiment, expensive and special coatings such as the anti-reflection film 23, which are conventionally required due to the provision of the gap, can be omitted, and the cost can be reduced, which is preferable.

Further, in the liquid crystal display device using the plastic substrate of the present invention, the adhesive layer has (e) an adhesive layer having a light-collecting function having a phase separation structure composed of at least two kinds of resins having different refractive indexes;

Or

(f) At least two kinds of resins having different refractive indexes (f1) or a resin layer in which a filler having a different refractive index from the resin is dispersed in the resin. (f 2) an adhesive layer having a light scattering function selected from

Alternatively, it is preferable that the adhesive layer is a combination of the above (e) and (f). By adding a method to achieve a general light-condensing function and light-scattering function to the adhesive layer, the light-scattering and light-condensing functions conventionally added to the adhesive layer 14 can be omitted, resulting in lower cost. It is preferable.

The adhesive layer has a phase-separated structure composed of at least two kinds of resins having different refractive indices, and as the adhesive layer (e) having a light-collecting function, It is also preferable to employ an adhesive layer in which many thin vertical layers of resin are alternately laminated. For example, light incident on the vertical layer of the high refractive index resin at an angle to the vertical surface is reflected at the boundary surface with the vertical layer of the low refractive index resin, and can be condensed. It is preferable because it can be brightened.

In another embodiment of the adhesive layer (e) having a light-collecting function and having a phase separation structure in which the adhesive layer is composed of at least two kinds of resins having different refractive indexes, the adhesive layer has a refractive index It is also preferable to employ an adhesive layer composed of an adhesive layer having a structure in which a number of thin vertical columnar layers of different resins are alternately arranged. For example, light incident on the narrow vertical columnar layer of high refractive index resin obliquely with respect to the vertical direction (length direction) of the columnar layer is also reflected at the interface with the thin vertical columnar layer of low refractive index resin. It is preferable because it can condense light and make the liquid crystal display surface brighter.

Further, the adhesive layer has a phase separation structure composed of at least two kinds of resins having different refractive indexes, and is an adhesive layer (f 1) having a light scattering function, wherein the resins having different refractive indexes have different refractive indexes. Of these, it is preferable to form an adhesive layer having a structure in which at least one resin is dispersed in the form of particles in another resin layer, since a light scattering function can be imparted to the adhesive layer. In addition, an adhesive in which a resin having a different refractive index from the resin constituting the adhesive layer is dispersed. The use of the layer (f 2) is preferable because the light scattering function can be further imparted to the adhesive layer.

As described above, by making the adhesive layer a specific adhesive layer, the anti-reflection layer, the light-collecting layer, and the light-scattering layer used as the adhesive layer of the polarizing film and the reflective film (including the semi-transmissive reflective film) can be formed. By simultaneously using the protective display cover or the light guide plate for the front light and the adhesive layer for the Z or pack light or the panel fixing holder, it is possible to achieve a reduction in cost and a reduction in the thickness of the film, which is preferable.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)

FIG. 1 is a sectional view showing a structure of a liquid crystal display device using a plastic substrate according to an embodiment of the present invention.

In FIG. 1, a liquid crystal display device has a liquid crystal cell 11 having a liquid crystal 11 a sandwiched between two plastic substrates 11 b having a pair of electrodes (not shown). A liquid crystal display panel 1 is provided as a liquid crystal display section including a polarization / phase plate 12 and a semi-transmissive reflection plate 13 provided through an adhesive layer 14. The liquid crystal display panel 1 and the liquid crystal display panel 1 are protected from external force. A transparent display cover made of glass, polycarbonate, acrylic resin or alicyclic olefin resin, etc., which has excellent mechanical strength, or a light guide plate for front light 2, which is disposed in close contact with the adhesive layer 3. It is.

The electrodes (not shown) are usually provided on the surfaces of the two plastic substrates 11b on the side where the liquid crystal 11a exists, respectively.

In the liquid crystal display device having such a configuration, a local point load external force such as when an iron ball is dropped is converted into a surface load that can be received by the entire liquid crystal display panel 1 by the adhesive layer 3. . Therefore, the liquid crystal display panel 1 Even if an external force is applied, the cell gap does not change locally, and the generation of bubbles in the liquid crystal cell 11 can be suppressed.

In addition, since the air gap of the air layer 22 having a certain thickness, which was conventionally provided between the display cover and the liquid crystal display unit, can be converted into a considerably thinner adhesive layer 3, it is possible to further reduce the thickness. It also eliminates the fact that the LCD display looks a little deep. Therefore, a clear and high contrast ratio liquid crystal display device can be obtained that makes full use of the mechanical properties of the plastic substrate, such as cracking, and the physical properties of lightness and thinness.

As the adhesive used for the adhesive layer 3, in addition to an adhesive which solidifies or cures after bonding, a pressure-sensitive adhesive called a so-called adhesive can be used. An adhesive, a silicone resin-based adhesive, an acrylic resin-based adhesive, a silicone resin-based adhesive, or the like is suitably used. The thickness of the adhesive layer 3 is not particularly limited, but is preferably 10 to 100 / im, more preferably 25 to 50 m.

Further, in the liquid crystal display device of the present invention, expensive and special coating such as the anti-reflection film 23, which is conventionally required due to the provision of the gap, is not required. At this time, the adhesive layer 3 can have an antireflection function by arranging a resin layer or the like having a multilayer structure composed of at least two kinds of resins having different refractive indices, thereby achieving cost reduction. Is possible.

FIG. 3 is a perspective view showing one embodiment of such an adhesive layer. In FIG. 3, the adhesive layer has a multilayer structure composed of two kinds of resins having different refractive indexes 3a and 3b. As for 3a and 3b, as long as one of the refractive indices is larger than the other, either one may be the upper layer. Further, a multilayer structure in which a plurality of units of 3a and 3b are repeated may be used. Here, the multilayer structure is a structure in which two or more layers parallel to the plane of the liquid crystal panel 1 are stacked. Therefore, arrow 5 is in the thickness direction. Examples of the combination of two kinds of resins having different refractive indexes used for the adhesive layer as described above include, for example, a combination of an acrylic resin adhesive and a silicone resin adhesive having a lower refractive index, or acrylic. A combination of a resin-based pressure-sensitive adhesive and a silicone resin-based pressure-sensitive adhesive having a lower refractive index than the resin-based pressure-sensitive adhesive is suitably used.

In addition, the light scattering function and / or the light condensing function added to the adhesive layer 14 such as the polarization / phase plate 12 and the semi-transmissive reflection plate 13 are bonded to the display cover or the light guide plate 2 for front light. It is also possible to adopt a configuration in which layer 3 is also used.

In this case, as the adhesive layer 3, for example, adhesive, it is shown in _c Figure 4, which may be such aspects of the adhesive layer shown in FIGS. 4 to 6 is a perspective view showing an embodiment of the adhesive layer The layer is an example of an adhesive layer (e) having a phase separation structure composed of two types of resins having different refractive indexes and having a light condensing function, and a thin vertical layer of each resin having a different refractive index. 3a and 3b are adhesive layers having a structure in which many are alternately laminated. The thickness direction of the adhesive layer is the direction indicated by arrow 5, and the vertical direction referred to as “thin vertical layer” is the direction indicated by arrow 5. Therefore, the plane of each of the vertical layers 3 a and 3 b is a plane perpendicular to the plane of the liquid crystal panel 1. If the refractive index of one of the thin vertical layers 3a and 3b is larger than the refractive index of the other, either of them may be a layer having a larger refractive index. By adopting the adhesive layer in such an embodiment, for example, light obliquely incident on the vertical surface of the vertical layer 3 a of the high refractive index resin is also formed at the boundary surface with the vertical layer 3 b of the low refractive index resin. It is preferable because it can be reflected and condensed, and the liquid crystal display surface can be made brighter.

An example of a combination of resins that can achieve a phase separation structure and form an adhesive layer having a different refractive index is, for example, an acrylic resin-based adhesive and a silicone resin-based adhesive having a relatively small refractive index as described above. Combination of agents, or acrylic resin adhesive and silicone resin with relatively small refractive index A combination of a system pressure-sensitive adhesive and the like is suitably used.

Next, the adhesive layer shown in FIG. 5 has a phase-separated structure composed of two kinds of resins having different refractive indices, and is another embodiment of the adhesive layer (e) having a light condensing function. This adhesive layer has a structure in which a large number of thin vertical columnar layers 3a and 3b of different resins having different refractive indexes are alternately arranged. The thickness direction of the bonding layer is the direction indicated by arrow 5, and the vertical direction of the “vertical columnar layer” is the direction indicated by arrow 5. Therefore, the vertical direction (length direction) of each of the columnar layers 3 a and 3 b is a direction perpendicular to the plane of the liquid crystal panel 1. Each of the columnar layers 3a and 3b may be a layer having a higher refractive index as long as one of the refractive indexes is higher than the other. By adopting the adhesive layer of such an embodiment, for example, light that is obliquely incident on the vertical columnar layer 3a of the high refractive index resin in the vertical direction (length direction) of the columnar layer can be formed of a resin having a low refractive index. This is preferable because it can be reflected and condensed on the boundary surface with the thin vertical columnar layer 3b, and the liquid crystal display surface can be made brighter.

An example of a combination of resins that can achieve a phase separation structure and form an adhesive layer having a different refractive index is, for example, an acrylic resin-based adhesive and a silicone resin-based adhesive having a relatively small refractive index as described above. A combination of agents or a combination of an acrylic resin-based pressure-sensitive adhesive and a silicone resin-based pressure-sensitive adhesive having a relatively small refractive index is preferably used.

The adhesive layer as shown in FIGS. 4 and 5, which has a phase-separated structure and is composed of two kinds of resins having different refractive indices, can be formed by using a method such as photolithography. That is, a uniform adhesive layer consisting of only one adhesive resin 3a is formed, and a mask is formed on the surface of the adhesive resin 3b at a position where the other adhesive resin 3b is to be formed. Cross-linking the areas not covered by the mask to the extent that the adhesiveness can be maintained, so as to differentiate the solubility of the parts where the mask exists and the parts where the mask does not exist in the solvent. It can be manufactured by removing the mask and removing the non-crosslinked portion with a solvent, and pouring the other adhesive resin 3b into the voids formed by the solvent. It is not limited to only. Next, in the adhesive layer shown in FIG. 6, in the resin layer 3a serving as an adhesive component, another resin serving as an adhesive component having a different refractive index from the resin constituting the resin layer 3a is formed into particles. Instead of the adhesive layer (f 1) having a dispersed phase-separated structure or other resin that is an adhesive component dispersed in the form of particles, the resin is included in the resin 3 a constituting the adhesive layer. By forming an adhesive layer (f 2) in which a filler having a different refractive index is dispersed, a light scattering function can be further provided to the adhesive layer. Each of the components 3a and 3b of the adhesive layer (f1) may be an adhesive resin having a higher refractive index as long as one of the components has a higher refractive index than the other. Examples of the combination of resins that can achieve such a phase-separated structure and form an adhesive layer having a different refractive index include, for example, the same acrylic resin-based adhesive and a silicone resin-based adhesive having a relatively small refractive index as described above. A combination or a combination of an acrylic resin-based pressure-sensitive adhesive and a silicone resin-based pressure-sensitive adhesive with a relatively low refractive index is preferably used. These two types of adhesives are well mixed and left to be compatible. Therefore, the other component is precipitated and dispersed in the form of fine particles in the layer of one component, and an adhesive layer having a structure as shown in FIG. 6 can be obtained.

Examples of the filler used for the adhesive layer (f 2) include silica fine particles, alumina fine particles, titanium oxide fine particles, and other resin fine particles that are not compatible with the adhesive used. It is obtained by mixing and dispersing fillers.

Further, it is also possible to use the adhesive layer (e) having the light-condensing function and the adhesive layer (f) having the light-scattering function as an adhesive layer as a light-concentrating and scattering layer. If the adhesive layer 3 has the light scattering function and the light collecting function as described above, the light scattering function layer and the light collecting function layer do not need to be separately provided, so that the cost is reduced. It becomes possible.

It is needless to say that the liquid crystal display device using the plastic substrate of the present invention can be applied without being influenced by the transflective display type and the reflective type display, and the monochrome and color display modes.

(Embodiment 2)

FIG. 2 is a sectional view showing a structure of a liquid crystal display device using a plastic substrate according to one embodiment of the present invention. The liquid crystal display device shown in FIG. 2 is provided with a lower member composed of (c) a light guide plate for backlight or (d) a holder 15 for panel fixing on the lower surface of the liquid crystal display device shown in FIG. The liquid crystal display section (liquid crystal panel 11) and the (c) backlight light guide plate or (d) panel fixing holder 15 are formed in the same manner as the adhesive layer described in the first embodiment. This is a liquid crystal display device arranged in close contact with the adhesive layer 3 of FIG. In the liquid crystal display device shown in FIG. 2, the portion above the semi-transmissive reflection plate 13 is the same as the liquid crystal display device shown in FIG. Description is omitted.

In the case of the liquid crystal display device having the structure shown in FIG. 2, when the upper member provided on the upper side of the liquid crystal display portion is (a) a display cover 2 for protecting the liquid crystal display portion from external force, The lower member provided on the lower side of the liquid crystal display section may be a combination of (c) a light guide plate 15 for backlight, and a light guide plate 15 for brightening the liquid crystal display section is provided. This is preferable because light from the backlight of the liquid crystal display device provided with a backlight such as a light emitting diode (LED) light source can be uniformly diffused to the lower surface of the liquid crystal display panel. When the upper member provided on the upper side of the liquid crystal display section is (b) the light guide plate 2 for front light, the lower member provided on the lower side of the liquid crystal display section is (d) It is preferable to use a combination of the panel fixing holders 15. In this case as well, the light guide plate 2 is provided so that the image on the liquid crystal display section can be made bright and easy to see, and the light guide plate for the front light also serves as (a) the display cover 2 and the light emitting diode (LED). ) It is preferable that light from the front light of a liquid crystal display device provided with a front light such as a light source can be uniformly diffused to the upper surface of the liquid crystal display panel.

To attach the backlight light guide plate or panel fixing holder to the display cover or the adhesive layer 3 used to bond the front light guide plate 2 to protect the liquid crystal display unit from external force and the lower side of the liquid crystal display unit. The adhesive layer 3 may be a mere uniform phase adhesive layer, or may be the same as described in the first embodiment, for example, any of the adhesive layers described with reference to FIGS. 3 to 6. Good. Further, as a material of the light guide plate for the backlight or the holder for fixing the panel, a transparent material formed of glass, polycarbonate, acryl-based resin or alicyclic olefin-based resin and having excellent mechanical strength is preferable. Used.

By adopting the mode described above, the external force of a local point load, such as when an iron ball is dropped, is converted into a surface load that can be received by the entire liquid crystal display unit by the adhesive layer. Since the members are similarly provided via an adhesive layer, the effect of reinforcing the entire liquid crystal display portion is exhibited, and the function of not locally changing the cell gap even when subjected to the external force as described above is sufficiently exhibited. Thus, the generation of bubbles in the liquid crystal cell can be suppressed, which is preferable.

(Comparative Example 1)

Liquid crystal using plastic substrate 11b in this embodiment shown in FIG. A display device and a liquid crystal display device having the same structure as the conventional liquid crystal display device using a glass substrate 20 shown in FIG. 7 but using the plastic substrate 11 b of the first embodiment instead of the glass substrate 20 To explain an example of comparison with a display device, an iron ball with a diameter of 11 mm was applied from the top of the display cover 2 to any point at any point for 5 seconds with a load of 0.2 MPa (2 kgf / cm ² ). After being pressed and left for 24 hours in an atmosphere of 80 ° C, the presence or absence of bubbles generated in the liquid crystal cell was visually observed. In the configuration of Embodiment 1 shown in FIG. Although it did not occur at all, it has the same structure as the liquid crystal display device using the conventional glass substrate 20 of FIG. 7, but instead of the glass substrate 20, the plastic substrate 11b of the first embodiment is used. In the liquid crystal display device using, bubbles with a diameter of about 5 mm were generated at all five points. Industrial applicability

According to the present invention, the liquid crystal display portion and the display cover or the light guide plate for front light, and further, the light guide plate for backlight or the holder for fixing the panel are disposed in close contact with the adhesive layer, so that bubbles in the liquid crystal cell can be obtained. No gaps are generated, and the gap between the display cover or front light guide plate and the liquid crystal display, which was conventionally provided, can be converted to a thinner adhesive layer, so that the overall thickness is further reduced. It is possible to eliminate the possibility that the LCD display looks a little deep. In addition, a clear and high-contrast liquid crystal display device can be obtained that makes full use of the mechanical properties such as cracking and the like, and the light and thin physical properties because a plastic substrate is used.

In addition, an antireflection function, a light scattering function or a light collecting function, or a combination thereof can be added to the adhesive layer, and cost reduction can be achieved.

Therefore, the field of mobile communication systems such as personal digital assistants and mobile phones It is useful as a liquid crystal display using a plastic substrate in terminals and the like used in the above.

Claims

Range of request

1. A liquid crystal display section that performs display using liquid crystal sandwiched between two plastic substrates each having a pair of electrodes, and (a) provided above the liquid crystal display section, to protect the liquid crystal display section from external force. For display cover or

(b) A liquid crystal display device comprising an upper member selected from a light guide plate for a front light, wherein the liquid crystal display portion and the upper member selected from the display cover (a) or the light guide plate for a front light (b). And a liquid crystal display device using a plastic substrate, which is disposed in close contact with an adhesive layer.

2. In addition, a lower member selected from (c) a light guide plate for backlight or (d) a holder for fixing the panel is provided below the liquid crystal display section, and the liquid crystal display section and the (c) backlight for the backlight are provided. 2. The liquid crystal display device using a plastic substrate according to claim 1, wherein a light guide plate or a lower member selected from (d) a holder for fixing a panel is disposed in close contact with an adhesive layer.

3. The upper member provided above the liquid crystal display section is: (a) a display cover for protecting the liquid crystal display section from external force, and the lower member provided below the liquid crystal display section is: (C) The liquid crystal display device using a plastic substrate according to claim 2, which is a light guide plate for a backlight.

4. The upper member provided above the liquid crystal display section is (b) a light guide plate for front light, and the lower member provided below the liquid crystal display section is

(d) The liquid crystal display device using a plastic substrate according to claim 2, which is a panel fixing holder.

5. The adhesive layer according to any one of claims 1 to 4, wherein the adhesive layer is an adhesive layer having an antireflection function formed of a resin layer having a multilayer structure composed of at least two types of resins having different refractive indexes. Using a plastic substrate as described

6. The plastic substrate according to any one of claims 1 to 4, wherein the adhesive layer is an adhesive layer having at least one phase separation structure selected from the following (e) and (f). A liquid crystal display using the same.

(e) an adhesive layer having a light-condensing function having a phase separation structure composed of at least two types of resins having different refractive indexes;

(f) A light scattering function selected from at least two types of resins having different refractive indices (f 1) or a resin layer (f 2) in which a filler having a different refractive index from the resin is dispersed in the resin. An adhesive layer having:

7. The adhesive layer has a phase separation structure composed of at least two kinds of resins having different refractive indices, and is an adhesive layer (e) having a light-collecting function and having the light-collecting function. 7. The liquid crystal display device using a plastic substrate according to claim 6, wherein the adhesive layer comprises an adhesive layer in which a number of thin vertical layers of respective resins having different refractive indexes are alternately laminated.

8. The adhesive layer has a phase-separated structure composed of at least two kinds of resins having different refractive indices, and is an adhesive layer (e) having a light-collecting function and having the light-collecting function. 7. The liquid crystal display device using a plastic substrate according to claim 6, wherein the adhesive layer comprises an adhesive layer having a structure in which a number of thin vertical columnar layers of resins having different refractive indexes are alternately arranged.

9. The adhesive layer has a phase-separated structure composed of at least two types of resins having different refractive indices, and is an adhesive layer (f 1) having a light scattering function. 7. The liquid crystal display device using a plastic substrate according to claim 6, wherein at least one kind of the resin comprises an adhesive layer having a structure dispersed in other resin layers in a particle form.