JPH1039287A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent liquid crystal display device capable of expanding a visual angle rapidly and largely and capable maintaing a satisfactory display grade without lowering display picture quality possessed by a liquid crystal cell, and which has high picture quality and a wide visual angle. SOLUTION: This liquid crystal display device is a liquid crystal display device to whose observation surface at least a microlens array sheet 61 is attached. The microlens array sheet 61 is such a array sheet that the diffusion degree at the time when a luminous flux is made incident from the normal direction of the face A of one side of the sheet, has a diffusion degree larger than that at the time when luminous flux is made incident in the normal direction of the face B opposite to the face A of the sheet and the microlens array sheet 61 is attached to the observation side of a liquid crystal cell 60 by making the face A of the array sheet 61 to be on the liquid crystal cell 60 side and the face B of the array sheet to be on the observation side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an excellent liquid crystal display device which satisfies both high image quality and a wide viewing angle.

[0002]

2. Description of the Related Art A liquid crystal display device uses an electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, fluidity, dielectric anisotropy, and the like, and can be used as an arbitrary display unit. Observes images displayed using an array of liquid crystal optical shutters that change the light transmittance and reflectivity by changing the alignment state of the liquid crystal by applying or applying an electric field. Devices, portable electronic devices, game machines, in-vehicle information display devices, and various information display devices.

As a display principle of a liquid crystal display device, a twisted nematic liquid crystal that performs display by controlling a voltage applied to a nematic liquid crystal layer twisted by about 90 degrees and combining a change in the optical rotation of the liquid crystal layer with a polarizing element is known. It is widely used because of its high display performance. However, the liquid crystal display device has a viewing angle dependency in which the display quality changes depending on the viewing direction, and in particular, in the case of twisted nematic liquid crystal, there is a problem that the display brightness is inverted or the color tone is changed, that is, a drawback that the viewing angle is narrow. there were.

It has been proposed in JP-A-5-249453 and the like that this disadvantage can be solved by providing an optical element such as a microlens array sheet on the observation surface of a liquid crystal display device.

Japanese Patent Application Laid-Open No. Hei 6-27454 proposes a method of obtaining a good display quality independent of an observation environment by combining a light shielding layer with a unit lens of a microlens array sheet.

[0006]

However, in such a conventional method, although the viewing angle is enlarged, the display contrast is lowered due to the diffusion effect of the microlens array sheet, and an image is not formed particularly in a high-definition display device having small display pixels. There are drawbacks related to display quality such as blurring.

The present invention solves the above-mentioned drawbacks, improves the viewing angle dramatically, and maintains high display quality without deteriorating the display quality of a liquid crystal cell. And an excellent liquid crystal display device having a wide viewing angle.

[0008]

The present invention employs the following means to solve the above-mentioned problems. That is, the liquid crystal display device of the present invention is a liquid crystal display device in which at least a microlens array sheet is mounted on an observation surface, and the microlens array sheet receives a light beam from a normal direction of one surface A. The diffusion degree in the case has a diffusion degree larger than the diffusion degree when a light beam is incident from the normal direction of the opposite surface B, and the surface A of the microlens array sheet is placed on the liquid crystal cell side, The liquid crystal cell is mounted on the observer side with the surface B facing the observer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of a detailed study of the drawbacks of the prior art, the present inventor has found that the degree of diffusion when measured in a specific direction of a microlens array sheet is an image quality when a liquid crystal display device is used. Found a strong correlation with
Further, in order to control the degree of diffusion, it is effective to provide a light-shielding layer corresponding to the unit lens array of the microlens array sheet, and to control the arrangement position and shape of the light-shielding layer. The present inventors have sought to solve the problem and arrived at the present invention.

In the present invention, a liquid crystal display device utilizes the electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, fluidity, dielectric anisotropy, and the like.
A display is performed using a liquid crystal cell which is an array of optical shutters that changes the alignment state of liquid crystal by applying or applying an electric field to an arbitrary display unit to change the light transmittance or the reflectance.

Examples of the mode of the optical shutter mechanism include a dynamic scattering mode (DS), a guest host mode (GH), a phase transition mode, a twisted nematic mode (TN), a ferroelectric mode, and a super twisted nematic mode (STN). ), Polymer dispersion mode, homeotropic mode and the like.

Further, as a method of driving each display unit of the liquid crystal cell, there are a segment drive for independently driving each display unit, a simple matrix drive for time-divisionally driving each display unit, a transistor, a diode and a plasma for each display unit. There is an active matrix drive in which an active element such as a gas chamber is arranged.

As a method of observing a liquid crystal display device, a reflective type in which a reflective layer having light reflectivity is provided on the back surface of the liquid crystal display device to reflect and observe light incident from the front surface of the liquid crystal display device, and a back surface of the liquid crystal display device There is a transmission type liquid crystal display device in which a light source is provided, and light emitted from the light source is transmitted through the liquid crystal display device for observation. In addition, there is a type that uses both of them. The liquid crystal display device of the present invention can be constructed by appropriately combining several display modes, drive modes, and observation modes as described above in accordance with the required characteristics. Twisted nematic mode, transmission type active matrix drive Twisted nematic mode, reflection type simple matrix drive Super twisted nematic mode liquid crystal display device, the effect of the present invention is great, furthermore, transmission type simple matrix drive super twisted nematic mode, transmission type active matrix drive The effect is great when the liquid crystal cell is in a twisted nematic mode.

The liquid crystal display device of the present invention has at least a microlens array sheet mounted on an observation surface.

In the present invention, the term "microlens array sheet" means a microunit lens, that is, a microunit unit having a lens function (hereinafter referred to as "microlens" or "unit lens") arranged in a plane. It is.

Here, "having a lens function" means that
Unlike a general monoconvex lens or monoconcave lens, it is not necessary to have a fixed focal point, but it is only necessary to have a function of refracting an incident light beam in an arbitrary controlled direction. Needless to say, so-called general `` diffusion plates '' and `` light scattering plates '', which are provided with light diffusing properties by disordered irregularities formed on the layer or surface to which light-scattering particles are added, randomly transmit incident light. Since it is scattered, it cannot be used in the present invention because it cannot be "refracted in any controlled direction" in the present invention.

The microlens array sheet used in the present invention has an interface between a first material layer in which a unit lens is sandwiched between two parallel planes and a second material layer having a refractive index smaller than the first material layer. Those that function as lenses by forming concave and / or convex shapes are preferable.

As the shape of the uneven surface, a one-dimensional lens array sheet in which a curved surface represented by a trajectory obtained by translating a curve such as a circular arc or an elliptic arc like a lenticular lens is arranged in one direction, a rectangular, triangular or hexagonal lens. There is a two-dimensional lens array sheet in which dome-shaped curved surfaces having a low surface such as a prism are arranged vertically and horizontally. Further, it may have a polyhedral shape in which planes and / or curved surfaces having various angles and curvatures are combined.

In this case, the first material forming the first material layer and the second material forming the second material layer are substantially transparent materials. As the first substance, a glass material, a transparent plastic material, or the like is preferably used. Also the second
As the substance, any substance having a refractive index smaller than that of the first substance may be used, and in addition to a glass material and a transparent plastic material, a liquid such as water or a gas such as air can be used.

The layers of such first and second materials are sandwiched between two parallel planes. The interface is a concave surface and / or a convex surface. By adopting such a shape, it is possible to obtain a viewing angle widening effect when a liquid crystal display device is formed.
A large viewing angle widening effect can be obtained by mounting the material layer side with the observer side.

In general, the viewing angle characteristic of a liquid crystal cell, that is, the change in display quality depending on the observation direction, is such that, even if the angle formed by the observation direction and the normal direction of the cell observation surface is constant, the observation direction is defined by the normal line as an axis. It is also caused by rotation. That is, the viewing angle is generally different depending on the direction in which the observation direction is moved from the front of the cell (left direction, right direction, upward direction, downward direction, etc., with respect to the display surface). Or,
Depending on the purpose of use of the liquid crystal display device, there is a case where the viewing angle in one direction should be preferentially expanded, such as to increase the viewing angle in the left-right direction. In such a case, the function of the lens of the microlens array sheet is changed to the viewing angle characteristics in each direction of the liquid crystal cell,
Alternatively, a liquid crystal display device with higher display quality can be provided by giving different characteristics to the desired viewing angle enlargement direction in each direction.

That is, when it is desired to enlarge the viewing angle characteristics in only one direction such as the vertical direction or the horizontal direction, a one-dimensional lens array sheet is used, and the unit lenses are mounted so that the arrangement direction matches the direction in which the viewing angle is desired to be enlarged. Can be achieved by: When it is desired to enlarge the viewing angle characteristics in two directions, there is a method in which two one-dimensional lens array sheets are superposed with an angle in the unit lens array direction, and a method using a two-dimensional lens array sheet. The lens shape can be controlled and designed so that the viewing angle in each direction is desired to be increased.

In the liquid crystal display device according to the present invention, the preferred relationship between the shape of the unit lens, the arrangement direction, and the mounting direction to the liquid crystal cell is such that the microlens array sheet is a one-dimensional micro array in which streak unit lenses are arranged in one direction. A lens array is used, and the unit lens arrangement direction of the lens array coincides with the liquid crystal alignment direction of the liquid crystal cell. This virtually eliminates the problem of viewing angles in all directions.

Here, “the liquid crystal alignment direction of the liquid crystal cell” means
When the liquid crystal cell to which no voltage was applied was observed from the normal direction of the observation surface, this is the direction in which the long axis alignment directions of each liquid crystal molecule were averaged. In other words, the liquid crystal layer was regarded as one birefringent body. This is the major axis direction of the refractive index ellipse. In the case of a twisted nematic liquid crystal, this direction coincides with the average alignment direction of liquid crystal molecules equidistant from both substrates in a liquid crystal layer sandwiched between two substrates.

Here, "matching" does not need to match exactly in one and only one geometrically defined direction in actual implementation, and a deviation of ± 10 degrees is allowed. This method is particularly effective when the liquid crystal cell uses a twisted nematic liquid crystal.

The size and position of the unit lens of the lens array sheet used in the liquid crystal display device of the present invention can be selected according to the size of the display unit of the liquid crystal cell. When the liquid crystal display device is of a dot matrix type, there are two preferable modes for the correspondence between one display unit and a unit lens. One is one for each display unit of the liquid crystal cell.
One unit lens corresponds exactly, and the other corresponds to one display unit, on average, two or more lenses. As a result, it is possible to suppress the occurrence of moire due to interference between the unit lens array pitch of the lens array sheet and the display unit pitch of the cells. Among these, the latter aspect does not require precise alignment, and improves productivity because the same microlens array sheet can be used for cells having several types of dot sizes. preferable. More preferably, four or more unit lenses correspond to one dot, and more preferably, eight or more unit lenses correspond to one display unit.

Here, the number n of unit lenses for one display unit is defined by the following equation (2) for a one-dimensional lens array sheet, and is defined by the following equation (3) for a two-dimensional lens array sheet. . n = N / (L / l) (2) n = N / (A / a) (3) where N is a unit on the display surface of the liquid crystal display device. The total number of lenses, L is the length of the one-dimensional microlens array sheet unit of the liquid crystal cell in the lens array direction, l is the length of one display unit of the liquid crystal cell in the lens array direction that contributes to display,
A is the area of the display surface of the liquid crystal display device, and a is the area of a portion contributing to display in one display unit of the liquid crystal cell. These equations show the average number of lenses corresponding to the display unit portion excluding the portion that does not directly contribute to the display such as the wiring space on the display surface of the liquid crystal display device.

In the liquid crystal display device of the present invention, a microlens array sheet is mounted on an observation surface. As a method for forming the microlens array sheet, a microlens array sheet is formed on a transparent substrate having high bending rigidity and is superposed on a liquid crystal cell. There is a method of attaching the microlens array sheet as described above, and a method of bonding the microlens array sheet to the liquid crystal cell observation surface. When the liquid crystal cell has a polarizing element on the observation surface side, a microlens array sheet can be disposed inside the polarizing element (on the liquid crystal layer side).

In the microlens array sheet, the interface between the first material layer in which the unit lens is sandwiched between two parallel planes and the second material layer having a lower refractive index than the first material layer has a concave surface and / or It functions as a lens by forming a convex shape, and when it is mounted with the second material layer side on the liquid crystal cell side and the first material layer side on the observer side,
A second material layer of the microlens array sheet, or
The top of the convex portion of the first material layer is formed of a substance having tackiness or adhesiveness, or a material layer having tackiness or adhesiveness is added to the surface of the second material or the top of the convex portion of the first material layer. In addition, a method of mounting the liquid crystal cell using the adhesiveness or the adhesiveness is used.

In the liquid crystal display device of the present invention, the diffusivity when a light beam is incident from the normal direction of one surface A (hereinafter, this is referred to as “positive diffusivity”, and is referred to as “φa”). ) Has a larger diffusion degree than the diffusion degree when a light beam is incident from the normal direction of the opposite surface B (hereinafter referred to as “reverse diffusion degree” and expressed as “φb”). It is necessary to use a lens array sheet. When a liquid crystal display device is configured by mounting such a microlens array sheet, in the microlens array sheet liquid crystal display device, the surface A of the microlens array sheet faces the liquid crystal cell and the surface B faces the viewer. To the observer side of the liquid crystal cell.

By adopting such a liquid crystal display device, it is possible to further preferably suppress the degree of image quality deterioration of the front image quality, which has been deteriorated in contradiction to the viewing angle expanding effect by mounting the microlens array sheet. it can.

In the present invention, the term “diffusion degree by the microlens array sheet” means that a luminous flux having a directivity angle of full width at half maximum and 6 degrees is incident on the microlens array sheet.
The observation angle is scanned from the opposite side of the incident surface with the incident light direction as a center, and the luminance observed from various directions is measured. At a certain observation angle χ (degree), １０-10 (degree), χ-5 (degree) ),
When the average luminance at five points of χ (degrees), χ + 5 (degrees), and χ + 10 (degrees) is defined as the diffused light luminance at the observation angle 拡 散, the diffused light luminance is at least の of the measured maximum diffused light luminance. Of the observation angles at which the maximum diffused light luminance is obtained, which is the absolute value of the difference between the observation angles at which the maximum diffused light luminance is obtained.

In the present invention, the terms "light beam", "luminous flux", and "refractive index" are 550 nm light beam, luminous flux and 550 nm refractive index, respectively, unless otherwise specified.

It is preferable that the reverse diffusion degree φb (degree) satisfies the following equation (1).

Tan φb ≦ 2p / d (1) where p (mm) is an array pitch of pixels constituting the liquid crystal cell, and d (mm) is a liquid crystal layer and a micro lens in the liquid crystal cell. Indicates the distance from the unit lens array surface on the liquid crystal cell side of the array sheet.

Further, the "liquid crystal cell-side unit lens array surface" is the surface of the lens layer functioning as a unit lens in the microlens array sheet which is closest to the liquid crystal cell, and the microlens array sheet is the first surface. In the case where the unit lens is constituted by the uneven surface of the material layer and the second material layer, the surface on the liquid crystal cell side of the two parallel planes on both sides of the uneven surface that contacts and does not intersect at least one point with the uneven surface. Becomes In the case where air is used as the material on the liquid crystal cell side, the liquid crystal cell-side unit lens array surface satisfies the above equation (1), which is a virtual plane in the atmosphere. The problem of the display device, that is, the “bleeding” of pixels, that is, a phenomenon in which a certain pixel is superimposed on an adjacent pixel and observed, thereby lowering the resolution of the display device and deteriorating the image quality, is a practical problem. It can be suppressed to an extent.

Further, it is preferable that the reverse diffusion degree φb (degree) satisfies the following expression (4). tan φb ≦ 3p / 2d (4) Here, each symbol is the same as that used in equation (1).

By satisfying the expression (4), "bleeding" can be almost completely eliminated.

Further, if the reverse diffusion degree φb (degree) is smaller than 5 degrees, not only the effect of maintaining the image quality is saturated, but also the light use efficiency is reduced, and the unit lens of the microlens array sheet is damaged. The required extremely high uniformity tends to be inferior, which is not preferable.

On the other hand, the forward diffusion degree φa (degree) is preferably 25 degrees or more. As a result, the problem of the viewing angle of the liquid crystal display device is solved to the extent that there is no practical problem. The angle is more preferably 35 degrees or more, whereby a liquid crystal display device in which the problem of “viewing angle” is almost completely solved can be provided.

In order for the microlens array sheet to have a characteristic in which the degree of diffusion is different depending on the light incident surface,
Although it can be achieved by designing the lens shape, the refractive index of each substance, and the like, the microlens array sheet preferably used in the liquid crystal display device of the present invention has a difference between the forward diffusivity and the reverse diffusivity. More than 10 degrees, even 2
Since it is preferable that the difference has a large difference of 0 degree or more, a method of combining a light shielding member corresponding to each unit lens is preferably used.

That is, the traveling path of the light beam entering from the surface A and having its traveling direction changed by each unit lens of the microlens array sheet and the traveling path of the light beam entering from the surface B and trying to reach each unit lens are tracked. However, a method of adding a light shielding member so as to block the light beam from the surface A as much as possible while blocking the light beam from the surface B is preferably adopted.

Hereinafter, one of the most preferable embodiments of the microlens array sheet used in the liquid crystal display device of the present invention, the microlens array sheet includes a first material layer and a second material layer having a smaller refractive index than the first material layer. A material layer is sandwiched between two parallel planes, and has a layer in which unit lenses having an optically convex shape are arranged by forming an interface between the first material layer and the second material layer into a periodic uneven shape. In the microlens array sheet, the degree of diffusion by the microlens array sheet when a light beam is incident from the normal direction of the unit lens array surface on the first material layer side is at least the unit lens in the in-plane direction of the microlens array sheet. It is regulated by a light-shielding layer in which the top of the projection is open,
The case where the light-shielding layer is provided on the first material layer side from the uneven surface of the microlens array sheet will be described in detail.

Here, the "light-shielding layer" means a layer having a function of absorbing and / or reflecting light rays passing therethrough. In this embodiment, the unit lens and the light-shielding layer are designed as follows.

First, the lens shape is set based on the forward diffusivity φa and the like from the viewing angle characteristics of the liquid crystal display device to be obtained, and then the reverse diffusivity φb is set based on the desired image quality. In general, φa is a point at which the unit lens uneven surface has the largest inclination with respect to the unit lens array surface (hereinafter, this point is referred to as “point P”).
In order to make φb smaller than this, a light-shielding layer is provided so that the incident light beam from the surface B does not reach this point P.

However, if the light-shielding layer blocks the incident light beam from the surface A, the efficiency becomes poor. Therefore, the unit lens is optically convex, that is, the uneven surface shape of the unit lens is the angle between the unit lens array surface on the first material layer side, which is a high refractive index material, and the contact surface at a certain point on the uneven surface. Is larger,
The uneven surface is preferably shaped so as to be located near the unit lens array surface on the first material layer side, whereby the light-shielding layer is formed so as to shield the light flux entering from the surface B and reaching the point P. Even if it is arranged, it is possible to prevent the light beam incident from the surface A from reaching the light shielding layer.

However, for the purpose of suppressing the generation of stray light due to light scattering on an optically discontinuous surface, a unit lens period of 2
If the width is less than 0%, it is also preferable that the optically concave or flat region is an uneven surface formed continuously with the optically convex region. From the required viewing angle φa
Is set, the maximum value of the angle of refraction (hereinafter referred to as the maximum value of the refraction angle on the uneven surface that the light-shielding layer must not block for the light flux that enters from the surface A, passes through the uneven surface, and passes through the microlens array sheet. “Α (degree)”). Further, when φb is set from the image quality to be obtained, the minimum value of the refraction angle (hereinafter, referred to as “below”) of the concave and convex surface which must be blocked by the light-shielding layer, out of the light flux incident from the surface B and reaching the concave and convex surface
This is called “β (degree)”. However, β ≦ α) is required.

Here, the “angle of refraction on the concave / convex surface” means the first angle when a light ray parallel to the normal direction of the unit lens array surface and incident from the second material layer travels inside the first material layer. The angle at which the traveling direction changes due to refraction on the uneven surface based on the refractive index difference between the material layer and the second material layer and the angle between the light traveling direction and the uneven surface.

In order to obtain the set values of φa and φb, it is preferable to provide a light-shielding layer that satisfies the following conditions (1) and (2) simultaneously.

Condition (1): When the microlens array sheet is viewed from the first material layer side in the normal direction of the unit lens array surface, the region where the refraction angle on the uneven surface exceeds β (degree) is a light shielding layer. Condition (2): The second lens parallel to the normal direction of the unit lens array surface
Among rays incident from the material layer side, rays whose refraction on the uneven surface of the unit lens is not more than α (degree) do not pass through the light shielding layer. These conditions will be described below with reference to the drawings.

FIG. 3 is a sectional view showing an example of a preferred embodiment of the unit lens constituting the microlens array sheet used in the present invention, wherein the first material layer 1 and the second material layer 2 are formed. It is sandwiched between two parallel planes, the first material layer side unit lens array surface 3 and the second material layer side unit lens array surface 4, and the interface between them is a convex and concave surface 5. This unit lens is defined as a normal 1 of the unit lens array surface on the first material layer side.
When viewed from the direction of 0, the region where the angle of refraction of the uneven surface exceeds α (degree) is defined by the normal line 10 and the traveling direction when the light traveling from the second material layer side is refracted by the uneven surface and proceeds. Are formed, that is, the regions 20 and 20 ′ on the uneven surface where the refraction angle 30 on the uneven surface is α (degree) or more.

According to the condition (1), in the microlens array sheet of the present invention, the regions 20 and 20 'must be covered with the light shielding layer. That is, a light-shielding band may be provided so as to cross each of the hatched regions 21 and 21 'in FIG.

Here, in the case where the concave / convex surface of the concave / convex surface is an irregular surface formed continuously with the optically convex region, the unit lens boundary region is also the same. Is preferably covered with a light-shielding layer in order to suppress the “bleeding” of the display when the liquid crystal display device is used.

Next, the condition (2) will be described. FIG. 4 shows FIG.
The unit lens is the same as that shown in FIG. 1, but a ray of light incident on the unit lens from the second material layer side in parallel with the normal direction of the unit lens array surface 4 and the refraction angle 31 on the uneven surface 5 is α (degree) ) Are the light ray 12 passing through the point 51 and the light ray 13 passing through the point 52 on the uneven surface. Points 51 and 5
Light rays that have passed through the uneven surface between 2 have a refraction angle α
The area through which these light rays pass is the area 22. From condition (2), since these rays must not pass through the light-shielding layer, the light-shielding layer should not be included in the region 23.

FIG. 2 shows an example that satisfies the conditions (1) and (2) simultaneously. FIG. 2 shows an example in which unit lenses having the same concavo-convex surface shape and refractive index as those of the unit lenses shown in FIGS. 3 and 4 are arranged on a transparent plastic substrate 7. And is not included in a portion corresponding to the region 22. In the case of the microlens array sheet shown in FIG. 1, since air is used as the second material layer, the unit lens array surface on the second material layer side is a virtual plane 4 in the atmosphere.

In order to increase the difference between the forward diffusivity and the reverse diffusivity, the position of the light-shielding layer in the thickness direction of the microlens array sheet is determined by setting the focal point distance of the unit lens to F. In this case, the distance is preferably 0.5F to 2.0F from the unit lens array surface on the first material layer side. Further, it is preferable that the focal point distance F is 0.5 times or more and 1.3 times or less of the unit lens width.

Here, the focal point distance means the distance between the unit lens array surface and the focal point assuming that the microlens array sheet has a sufficient thickness.

Further, the "condensing point" here means that the light beam incident on the unit lens from the normal direction on the second material layer side of the microlens array sheet is condensed by the unit lens, and the light beam density becomes highest. A point (in the case of a one-dimensional lens array, this is a “line”, but here, according to a custom, this is also referred to as a “condensing point”).

Further, in order to realize a large viewing angle enlarging effect and a function of maintaining image quality, the focal point distance is set to 1.0 times or less of the unit lens width, and the width of the opening of the light shielding layer is set to １ ／ of the unit lens width. It is preferable to set the following.

The end of the light-shielding layer is a light ray that is parallel to the normal direction of the unit lens array surface and is incident from the second material layer side and is refracted most at or near the edge of the unit lens. It is preferable to be on the side of the uneven surface from the intersection Q of the two light beams. Thus, when the liquid crystal display device is used, a light beam can be emitted in a deeper viewing angle direction. Here, “being on the uneven surface side from the intersection point P” means that there is a space between the flat surface including the intersection point P and parallel to the unit lens array surface and the uneven surface.

When the unit lens is symmetric, the angle at which the maximum refracted ray at one edge is refracted on the uneven surface and the angle at which the refracted ray is refracted at the other edge have the same value. If the unit lens is asymmetrical on the center line of the lens but the unit lens is asymmetric, the angle of refraction of the maximum refraction ray at one edge may be different from the angle of refraction at the other, and in this case, the intersection Q
Does not coincide with the center line of the unit lens.

In the present invention, the term "light-shielding layer" means a layer having a function of absorbing and / or reflecting light rays passing therethrough. However, in view of the appearance of a liquid crystal display device, it absorbs visible light. It is preferable that

Such a light-shielding layer can be composed of a known material such as a metal film and an oxide thereof, and a resin composition to which a pigment or a dye is added. It is preferable that the liquid crystal display device absorbs visible light from the viewpoint of the appearance of the liquid crystal display device.

The color tone of the light-shielding layer is preferably substantially achromatic, that is, black. In order to obtain such a color tone, a pigment obtained by adding a pigment such as carbon black or titanium black or a black dye to a resin composition is preferably used. Further, when a dye is used here, it is preferable to use a black dye having a light fastness of 5 or more from the viewpoint of light fastness, and further, an azo black dye from the viewpoint of dispersibility, solubility, versatility and the like. It is most preferred to use

As the shape of the light-shielding layer, any of a flat film shape and a three-dimensional shape proposed in JP-A-7-72809 can be used.

The light-shielding ability of the light-shielding layer is expressed as an average of the entire light-shielding band and expressed as an average visible light transmittance after visibility correction of 0.5 from the viewpoint of efficient use of the light flux from the liquid crystal cell to be combined. %, Preferably 20% or less, more preferably 10% from the viewpoint of suppressing external light reflection.
The following is preferred.

This light-shielding layer is preferably provided on the first material layer side from the uneven surface. When the light-shielding layer is not a flat film but a three-dimensional irregular cross-section such as a triangle or an inverted T-shape, a part of the light-shielding layer is in contact with the uneven surface or protrudes toward the second material layer. However, it is preferable that at least the widest part is on the first material layer side, and it is preferable that the light-shielding layer and the uneven surface are not in contact with each other.

A surface which becomes an observation surface when the microlens array sheet is mounted on the liquid crystal cell, for example, a surface opposite to the surface 3 provided with the light shielding layer 6 of the transparent plastic substrate 7 in the configuration shown in FIG. The surface 8 can be subjected to a surface hardening treatment, an anti-reflection treatment, an anti-glare (non-glare) treatment or the like, as required on the surface of the observation surface of the conventional liquid crystal display device, if necessary.

The light-shielding layer is preferably embedded in the microlens array sheet in that the mechanical strength of the microlens array sheet can be increased and the microlens array sheet can be easily handled. For this purpose, there are a method of embedding a light shielding layer inside the first material layer, and a method of forming each layer on a separately prepared transparent substrate in the order of light shielding layer / first material layer / second material layer.

The microlens array sheet of the present invention
It can also be made using a transparent sheet or film as a substrate. At this time, it is preferable to use a flexible plastic film as the substrate from the viewpoint of handleability and impact resistance when the liquid crystal display device is used. As such a plastic film, a polyethylene terephthalate film, a polycarbonate film, a polyarylate film, a polysulfone film, an acrylic resin film and the like are preferably used.

When the liquid crystal display device of the present invention is a transmissive liquid crystal display device having a back light source, it is preferable that the back light source has directivity in the normal direction of the light emitting surface. Thereby, a light beam emitted from a light source such as a fluorescent tube can be effectively used.

That is, in the liquid crystal display device of the present invention, the individual unit lenses of the lens array sheet refract a light beam transmitted in a direction in which the display quality of the liquid crystal cell is inferior so as not to affect the observation, or to shield light. At the same time as being absorbed or reflected by the layer, the luminous flux transmitted in the direction showing good display can be observed from various directions. The light flux emitted at a large angle with respect to the normal direction of the display surface is not used. Therefore, by giving directivity to the light beam emitted from the rear light source, the light beam emitted from the light source can be used effectively.

Therefore, the directivity of the back light source is 30
Degree or less. On the other hand, it is preferable to set the directivity to 2 degrees or less, since the structure of the back light source becomes complicated, but the above-mentioned effect is practically eliminated and a high degree of uniformity is required for the microlens array. Absent.

Here, the “directivity” means that when a certain point on the rear light source is tilted from the direction showing the maximum brightness to the direction of arrangement of the minute unit lenses, the brightness becomes half of the maximum brightness. Represents the angle of

In order to provide a rear light source having such directivity, a light beam emitted from a light source such as a fluorescent tube is converted by using a means such as a Fresnel lens or a Fresnel prism, or by combining a minute reflecting surface as a reflecting mirror. There are, but not limited to, means using a multi-reflector, and among these, a micro lens or a lens is used because the light emitted from a light source such as a fluorescent tube is effectively used and the thin and light weight is easily achieved. It is preferable to provide a Fresnel sheet in which micro prisms are arranged in a sheet shape on a light emitting surface close to a liquid crystal cell of a back light source.

FIG. 1 is a schematic view of a liquid crystal display device for explaining an example of the configuration of the liquid crystal display device of the present invention. A microlens array sheet 61 is provided on the observation surface side of the liquid crystal cell 60, and a back light source 62 is provided on the back of the liquid crystal cell.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but is not limited thereto.

(A) Preparation of Microlens Array Sheet A mold in which a large number of curved grooves are engraved in parallel (the pattern pitch is 43 μm, the groove depth is 13.5 μm, and the groove depth is 19.5).
Two types of μm, the size of the engraved part is 300mm x 50
A 0 mm flat stamper) is filled with an ultraviolet curable resin (refractive index of 1.50 after curing), and a transparent polyester film "Lumirror" (manufactured by Toray Industries, Inc., thickness 6 μm, 25 μm) as a flat transparent substrate is further filled thereon. , 38 μm,
After laminating a film coated with a 2 μm-thick easy-to-adhesive coating material on a 300 μm width), use a rubber roller to remove excess UV-cured resin from above the polyester film so that the ridge of the mold contacts the polyester film. Ironed out and the film was brought into close contact with the mold.

A commercially available black resist added with carbon black (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the film surface of the obtained mold / ultraviolet effect resin layer / film laminate using a spin coater and dried. Ultraviolet light was exposed by a high-pressure mercury lamp through a photomask having a striped pattern (pattern pitch: 43 μm), and an uncured portion was dissolved and removed by a developer.

At this time, the center line of the opening of the light-shielding layer coincides with the ridge line of each unit lens by overlapping the mold with the alignment mark written on the photomask. 10 μm width, 13 μm, 2
A light-shielding layer having a thickness of 3 μm was formed and removed from the mold to produce various microlens array sheets.

Further, a microlens array sheet partially having no light-shielding layer was prepared.

Next, the light shielding layer side of the microlens array sheet obtained here (the one without the light shielding layer is
The film side) was bonded to a 0.8 mm thick acrylic flat plate (transparent plastic substrate).

The characteristics of the various microlens array sheets thus obtained are summarized in Table 1. Table 1
In the above, the "gap" of the "position of the light shielding layer" indicates the distance between the unit lens array surface on the first material layer side and the light shielding layer forming surface. Similarly, in Table 1, “correspondence to conditions” means “○” when the formed light-shielding layer satisfies the above-described conditions (1) and (2), and “x” when the formed light-shielding layer does not satisfy the above conditions (1) and (2), respectively. Indicated by.

The microlens array sheet used in Example 1 has the concavo-convex surface shape and the light-shielding layer disposing position shown in FIG. 2 in which the light incident from the normal direction of the microlens array sheet becomes one straight line. This is a one-dimensional microlens array in which a part of a non-cylindrical side surface having a cross section expressed by a 6th order equation is arranged in one direction so as to condense light. The focal point distance of the unit lens of this microlens array sheet is 2
9 μm.

(B) Preparation of Liquid Crystal Display Device A twisted nematic liquid crystal TFT color display (9.5 inches diagonal, 480 pixels in length × 640 dots in width, with backlight) mounted on a commercially available personal computer is liquid crystal. The microlens array sheet prepared in (1) was mounted on the observation surface side of the liquid crystal cell with the lens forming surface facing the liquid crystal cell to obtain a liquid crystal display device. At this time, the unit lens arrangement direction of the microlens array sheet was the screen vertical direction which is the liquid crystal alignment direction of the liquid crystal cell.

This liquid crystal cell has a thickness of 1.10 as a substrate.
mm glass plate is used, and a polarizing element having a thickness of 0.16 mm is adhered. Therefore, the distance d between the liquid crystal layer and the unit lens array surface on the liquid crystal cell side of the microlens array sheet is d.
Became 1.26 mm. The pixel arrangement pitch p
Is 0.30 mm.

(C) Evaluation A test pattern composed of three colors “white”, “50% gray” and “black” was displayed on the liquid crystal display device thus obtained, and observed from the viewing angle and from the front. The image quality at the time was evaluated according to the following criteria. The evaluation was performed in a dark room. The results are shown in Table 1.

[A method of evaluating characteristics] (A) Viewing angle When the luminance of the display surface was measured by scanning the observation direction in the vertical direction of the screen from the normal direction of the observation surface of the liquid crystal display device,
The brightness of the area where “50% gray” is displayed is “white”
The viewing angle range in the range of 20% to 80% with respect to the luminance of the region where is displayed was defined as the viewing angle. This indicates a viewing angle range in which the display of “halftone” is observed as “halftone”.

At this time, if the luminance of the "white" display area is 5% or less of the luminance in the normal direction, the viewing angle up to this observation angle is used.

(B) Contrast ratio The contrast ratio (the luminance of the “white” display area relative to the luminance of the “black” display area) when observed from the front (normal direction) of the observation surface of the liquid crystal display device is shown.

(C) Bleed When each pixel can be observed independently of adjacent pixels, it is evaluated as “「 ”. When it cannot be observed independently of other pixels, it is evaluated as“ X ”.

As can be seen from the table, in the liquid crystal display device of the present invention, even with a microlens array sheet using the same microlens group, the viewing angle is widened and the image quality deterioration (contrast ratio deterioration) is small. We can see that we can do it. In particular, those in which the light-shielding layer is appropriately arranged are such that a good image can be observed from virtually any direction, and the contrast ratio is high, and a wide viewing angle without blur and good image quality can be obtained. You can see that.

[0093]

[Table 1]

[0094]

According to the present invention, the disadvantage that the viewing angle of the conventional liquid crystal display device is narrow by the simple operation of mounting the microlens array sheet on the observation surface is obtained.
The problem can be solved while maintaining the image quality.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of a liquid crystal display device of the present invention.

FIG. 2 shows an example of a cross section of a microlens array sheet preferably used in the present invention.

FIG. 3 is a diagram illustrating a condition (1).

FIG. 4 is another diagram illustrating the condition (2).

[Explanation of symbols]

 1: 1st material layer 2: 2nd material layer 3: 1st material layer side unit lens arrangement surface 4: 2nd material layer side unit lens arrangement surface 5: uneven surface 6: light shielding layer 7: transparent plastic substrate 8: transparent Surface of the plastic substrate 10: normal to the unit lens array surface 11: normal to the uneven surface 12: light beam with a refraction angle of β (degree) 13: light beam with a refraction angle of α (degree) 14: refraction angle of α Another light ray that becomes (degree) 15: a light ray whose refraction angle is less than α (degree) 21, 21 ′: a region that satisfies the condition (1) 22: a region that satisfies the condition (2) 30: a refraction angle on an uneven surface (Β) 31: Refraction angle (α) on uneven surface 50: Point on uneven surface 51: Point on uneven surface 52: Edge of light shielding layer 60: Liquid crystal cell 61: Microlens array sheet 62: Back light source

Claims (7)

[Claims] 1. A liquid crystal display device in which at least a microlens array sheet is mounted on an observation surface, wherein the microlens array sheet has a diffusivity when a light beam enters from a normal direction of one surface A. The micro lens array sheet has a diffusivity larger than that when a light beam is incident from the normal direction of the opposite surface B, and observes the surface B of the microlens array sheet on the liquid crystal cell side and the surface B. A liquid crystal display device, wherein the liquid crystal display device is mounted on a viewer side of a liquid crystal cell on a viewer side. 2. The liquid crystal display device according to claim 1, wherein the degree of diffusion φb (degree) when a light beam is incident from the normal direction of the surface B satisfies the following expression (1). tan φb ≦ 2p / d (1) (where p (mm) is an array pitch of pixels constituting a liquid crystal cell, and d (mm) is a liquid crystal layer and a microlens array sheet in the liquid crystal cell) Represents the distance from the liquid crystal cell side unit lens array surface) 3. The liquid crystal display device according to claim 1, wherein a diffusion degree φa (degree) when a light beam is incident from the normal direction of the surface A is 25 degrees or more. 4. The microlens array sheet is sandwiched between two parallel planes of a first material layer and a second material layer having a smaller refractive index than the first material layer. 4. The method according to claim 1, wherein the second material layer has a layer in which unit lenses having an optically convex shape are arranged by forming a periodic uneven shape at the interface. The liquid crystal display device as described in the above. 5. The microlens array sheet having a degree of diffusion when a light beam is incident from the normal direction of the unit lens array surface on the first material layer side at least in the unit lens convex direction in the microlens array sheet plane direction. 5. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is regulated by a light shielding layer having an open top. 6. The liquid crystal display device according to claim 4, wherein the light shielding layer is provided on the first material layer side with respect to the uneven surface of the microlens array sheet. 7. The microlens array sheet according to any one of claims 4 to 6, wherein the microlens array sheet is mounted on a liquid crystal cell observation surface with the first material layer side being the observation surface side and the second material layer side being the liquid crystal cell side. 3. The liquid crystal display device according to 1.