KR20080090636A - A back-coated optical sheet formed with various size of micro lens - Google Patents

Abstract

An optical sheet with microlenses and a back coating film are provided to increase a haze by suppressing a simple transmittance or simple refraction by reducing a hollow space between main scattering lenses. An optical sheet includes a main microlens(701) and a sub microlens(702), which are arranged on the same optical surface to scatter light. The main microlenses are arranged in a lattice formation. Sub microlenses are arranged at center points inside a closed polygon, which is formed by connecting center points of the main microlenses with apices of the lattice. The sub microlenses are alternatively arranged with respect to each other. A sum of mean diameters of the main and sub microlenses is smaller than a mean diagonal line or a mean height of the closed polygon. The sum of mean diameters of the main and sub microlenses is greater than the mean perimeter of the closed polygon divided by the number of apices of the closed polygon.

Description

A back-coated optical sheet formed with various size of micro lens

1 is a cross-sectional structure diagram of a flat panel display device (liquid crystal display device).

2 is a cross-sectional view of a conventional light diffusion sheet.

Figure 3 is a cross-sectional view of the optical sheet (lens molding) in the previous step of the present invention.

4 is an external perspective view of the optical sheet of FIG.

5 is a plane photograph of the optical sheet of FIG.

Figure 6 is a plan view of the lens array of the optical sheet of the present invention.

7 is a plan view of a modified lens array of the optical sheet of the present invention.

8 is a cross-sectional view (molding lens type) of the optical sheet of the present invention.

9 is a (bead insertion type) cross-sectional view of the optical sheet of the present invention.

FIG. 10 is a diagram showing light scattering, transmittance, and light amount distribution of the optical sheet of FIG. 3.

11 is a light scattering, transmittance and amount distribution of the optical sheet of the present invention

12 is a contact view of the optical sheet base layer of the present invention and the light guide plate.

Figure 13 is a laminated view of the optical sheet of the present invention.

14 is a contact view of the optical sheet base layer and the prism sheet protrusion of the present invention.

Figure 15 is a photograph of the back coating portion of the optical sheet of the present invention.

Figure 16 is a photograph of the back coating portion (including protrusion dimensions) of the optical sheet of the present invention.

[Description of reference numerals for the main parts of the drawings]

10, 723: light guide plate 12: light source

16,18,128,500,703: Diffusion sheet 17,18,733: Prism sheet

19: liquid crystal panel 22: reflector

23: polarizer

524, 701: main micro lens 702: sub micro lens

704: empty space (flat surface)

703: molding portion 713: base layer

705: overlapped sub-micro lens

706: sub micro lens surrounded by three main lenses

711: back coating bumps (beads)

The present invention relates to an optical sheet, and in particular, to the main and sub-micro lens array structure and the back-coated surface structure of the optical sheet.

Since the backlight assembly of a general liquid crystal display device basically emits light to one or more point light sources at the time of first light emission, the optical member diffuses the point light source to the surface light source and condenses in the direction as perpendicular to the liquid crystal array plane as possible. Is needed.

The optical member performs functions such as light condensing, diffusion, and polarization, and is generally formed in a thin plate shape such as a film form (optical film) and a sheet form (optical sheet).

Among the optical members, when looking at a plate-shaped optical sheet having a constant thickness and intensity, a plurality of light collecting sheets, beads, or microlenses are arranged in order of a prism shape to perform light collecting functions. There is a diffusion sheet, etc. to be performed, these are used in combination with a polarizing sheet, a protective sheet is laminated in one or more.

1 is a cross-sectional view illustrating a configuration of a backlight assembly of a general liquid crystal display device.

Referring to the backlight assembly illustrated in FIG. 1, there is a light source 12 serving as an initial light emitting unit, and a light guide plate 10 for guiding light emitted from the light source 12 to the opposite end, wherein the emitted light is a reflecting plate 22 positioned below. ) Is reflected and re-reflected by the reflective structure surface 13 or the like and is incident on the optical member located on the upper surface.

Since the light incident on the optical member through the light emitting unit is not yet uniform and the brightness is not even to enter the liquid crystal panel, the directivity and uniformity of the light through the optical sheet unit including the diffusion sheets 16 and 18 and the light collecting sheet 17 and the like. To improve.

That is, the upper part of the light guide plate 10 is provided with a plurality of optical sheets for improving the efficiency of the light guided by the light guide plate, the light rays incident from the point light source through the multi-reflection in the light guide plate, that is, A diffuser sheet may be arranged, which may evenly scatter low-density and coarse light rays, followed by a condenser sheet having a prism shape of the protrusion cross section—and again a diffuser sheet (or protective sheet). Here, the diffusion sheets 16 and 18 scatter the incident light so as to evenly distribute the brightness of the light, and the light condensing sheet in the direction perpendicular to the sheet surface as perpendicular to the sheet plane as possible to improve the light distribution. The light is collected again to increase the brightness of light per unit area.

However, in order to convert light as brightly and evenly as desired in the above process, it is necessary to pursue the maximum diffusion effect and the light collection effect with the minimum optical sheet. In other words, it is only necessary to arrange several diffusion sheets for the diffusion effect, but this increases the cost of the product and also decreases the transmittance of light due to the increased sheet thickness and the spaces between the sheets, thereby decreasing the brightness of the entire screen.

On the contrary, if the overall thickness of the diffusion sheet is reduced by considering only the light condensing effect, the luminance increases, but the uniform distribution of light is difficult to achieve, resulting in a haze of the entire screen.

In addition, when the sheets are laminated in order to improve the optical properties of the optical sheets, friction of the upper and lower surfaces of the sheets increases, resulting in surface damage, scratches, and the like, and the quality of incident light to be collected / diffused is also reduced.

In order to solve the above problems, the optical sheet according to the present invention forms a light scattering part with a single medium such as a resin to ensure transmittance at the prism sheet level, more specifically, the shape of the micro lens part responsible for the light diffusion role and Improved alignment to achieve maximum light diffusing efficiency within a single sheet, and back-coating on the back of the optical sheet in the range where the overall optical properties are reduced to a minimum, reducing adhesiveness and friction between laminated surfaces and back light assembly When assembling the sheets in the assembly process, or when storing or transporting the sheets in front of the assembly production, to improve the surface properties of the back of the sheet so as not to damage the smooth and sensitive sheet surface.

The present invention for achieving the technical problem of the invention as described above has the following main technical features.

First of all, the optical sheet of the present invention is arranged by densely adjusting the size of the microlenses, the microlenses are arranged densely, eliminating the flat surface between the main microlenses that the light refraction and scattering (and a part of total reflection) is less than the lens surface as possible The submicrolenses are smaller in size than the main microlenses so as to increase the overall optical interface.

Next, the micro lens structure may be a mono-layer that forms a lens shape on a base film resin as it is, or a bead is inserted into the lens part to form a complex structure.

Finally, the backing layer may further include a back-coating portion in which microprotrusions or microbeads are randomly inserted into the bottom surface of the optical sheet, that is, on the opposite surface of the lens forming surface.

Although the main technical features of the present invention will be described in more detail based on the background of the present invention and one embodiment described in the drawings, the technical spirit of the present invention is limited by the embodiments and detailed structures thereof shown in the following drawings. Notify in advance.

Figure 2 is a conventional diffusion sheet of the optical properties of the optical sheet of the present invention, performing the light diffusion function mainly. Referring to the diffusion sheet of FIG. 2, the light diffusion parts 220 and 224 are disposed on both upper and lower sides of the base sheet 222, and the light diffusion parts are beads embedded in the beads, and may be made of glass. In general, the density of the transparent plastic resin surrounding the surroundings is higher, and thus the refractive index of the transmitted light is further increased (hereinafter referred to as 'bead') to scatter the light incident therethrough. In the case of the diffusion sheet, the beads are arranged in double, so that the entire optical interface is very large, so that the light diffusing effect is satisfactory, whereas the direct light ability is degraded due to the large optical interface. In order not to deteriorate, it is necessary to further laminate | stack and use a light collecting sheet (for example, a prism sheet). Of course, in this case, as the optical sheets are stacked, the overall transmittance as well as the increase in manufacturing cost due to the complexity of the structure, regardless of diffusion and condensation, will gradually decrease.

3 is a view of forming a spherical lens portion (micro lens portion) directly on the upper forming layer of the optical sheet instead of an inherent refractive element (bead) having abundant scattering property to improve the low linearity of FIG. It corresponds to the previous step.

3, the refractive index or scattering degree of the unit lens element may be lower than the refractive index or scattering degree of the unit bead element if the optical sheet of FIG. 3 is viewed only in terms of the self-retained refractive index of the base film (for example, resin, etc.), which is a molding material of the lens. As shown in FIG. 2, the diffusivity of the entire incident light is considerably reduced because of being a single arranged hemispherical scattering device, rather than a multi-arranged spherical scattering device. Can be used.

4 and 5 are drawings (and photographs) illustrating the optical sheet shown in FIG. 3 in more detail, respectively, and represent an external perspective view and a top image.

4 and 5, there is a flat empty space between the micro lens units 524, that is, a space where the flat portion of the optical sheet 500 is exposed due to geometric limitations due to the hemispherical lens arrangement. Is not total reflection or scattering, only simple refraction. (See FIG. 10)

FIG. 10 briefly illustrates a transmission mechanism of incident light in the optical sheet of FIGS. 3 to 5. The upper curve of FIG. 10 shows the distribution and intensity of light, which is very helpful for light diffusion in the flat part, not the micro lens part. Only one-way refraction will fail.

In this case, since the desirable phenomenon such as multi-directional refraction and total refeltion occurring in the micro lens unit does not occur at all on the flat surface, the luminance is slightly lowered, and above all, the uniformity of light (e.g., light and dark of light is distributed). Degree- haze: This is called 'haze'. Therefore, it does not exhibit the desired balanced performance as an optical sheet.

3 to 5 and 10, the lens arrangement that can be implemented to overcome the limitation of the required performance due to the partial flat surface in the optical sheet arrayed with a single size of the micro lens as in Figure 6 corresponding to the embodiment of the present invention 7 is a lens array.

In the optical sheet of FIG. 6, the upper molding sheet part 703 has a main microlens 701 arranged in a square, and has a sub-sized size smaller than the main microlens at an approximately center position of a square formed by the centers of the four main microlenses. Micro lenses 702 are arranged.

By the way, the microlenses have an extremely small element shape of only a few micrometers to several tens of micrometers, so they may be ideally arranged as shown in FIG. 6 in the actual molding process, but as shown in FIG. 704 or an array 705, a position 706 on the center of the triangle or hexagon may be implemented. However, since the same phenomenon occurs in the single-size microlens array of FIG. 5, the configuration of FIGS. 6 and 7 which further apply the sub-microlens array is considered to be the configuration of FIGS. Is a clear difference in the haze.

In FIG. 7, if the arrangement state of the main micro lens (or main lens) and the sub micro lens (sub lens) is geometrically defined, the center points of each of the four (rarely three) main lenses are drawn as vertices. The sub-lens is positioned at an approximately center position of the closed polygon, and the length of the sum of the diameter of the sub-lens (d2) and the diameter of the main lens (d1) is greater than the length of one side of the closed polygon, and the diagonal length of the closed polygon or It becomes smaller than the height.

In this case, the diagonal length or height minus the diameter of the main lens (L1 or L2) is the theoretical maximum diameter at which the sub-lens can be formed, and the value of the length of one side minus the diameter of the main lens (L3) is between the main lenses. It becomes the actual minimum diameter (the theoretical minimum diameter is 0) of the sublenses, which serves to fill the empty space.

If the geometric arrangement is described in terms of extending from one dimension to three dimensions, the micro lenses are optical elements (for example, a hemispherical first optical element (main micro lens) and a second optical element (sub) which are points in one dimension. Microlenses), and then the first optical element and the second optical element are alternately arranged alternately to form one optical line (one-dimensional line), and then the optical line is continuously Arranged to form one optical surface, and next to the point where the first optical element of one optical line is located, an optical surface arranged to position the second optical element of another optical line (two-dimensional surface). It can be represented by the optical sheet (three-dimensional solid) which makes an optical surface an upper surface.

The size of the second optical element may be selected within a range smaller than the size of the first optical element and larger than a minimum adjacent distance between the first optical elements on the optical surface.

FIG. 11 illustrates a transmission (and diffusion) mechanism of incident light implemented by the main-sub lens array of FIG. 6 or 7.

Referring to FIG. 11, in view of two aspects of the distribution of light quantity and intensity (luminance), unlike FIG. 10, the total amount of refraction and scattering is changed by changing a flat surface existing between lenses of the upper molding sheet to an additional lens surface. As a result of the large increase and a slight increase in total total reflection, as a result, the luminance is slightly increased, and in particular, the haze is significantly increased as compared with the conventional optical sheet.

As a result, the structure of the present invention, in which the sub-microlenses in FIG. 6 (or FIG. 7) are additionally arranged, consequently exhibits excellent diffusion performance and luminance maintaining performance than FIG. 10.

FIG. 8 illustrates a surface in which the cross sections of the main microlens and the submicrolens of the optical sheet of the present invention are simultaneously exposed (that is, a cross section of FIG. 7 diagonally), where the main microlens 701 has a maximum average height h1 and an average. It can be defined as a generally hemispherical shape with a radius r1 (so small that it is not geometrically accurate hemispherical shape), and the size or preferred design dimension applied to the actual product is 2 * h1 ≒ 2 * r1 ≒ 20 ~ 70㎛ ( Average diameter of a large sphere).

In addition, in FIG. 8, since the maximum average height h2 and the average radius r2 of the sub microlens 702 play an auxiliary role between the arrangement spaces of the main lenses, it is necessary to design a dimension that places more emphasis on transmission inhibition than diffusion. As the size or preferred design dimension applied to the product, it can be applied as 2 * h2 ≒ 2 * r2 ≒ 1 ~ 20㎛ (mean diameter of small sphere).

FIG. 9 illustrates a cross-sectional structure of a main-sub micro lens unit including a lens unit by inserting a bead instead of the lens molding structure of the base film unitary material of FIG. 8, wherein the size of the beads is the dimension of each lens of FIG. 8. There will be a slight difference compared to, but it is a negligible size difference in engineering, so the main bead can be chosen to be about 20 to 70 μm and about 1 to 20 μm.

In addition, the resin coating surface surrounding each bead may not be coated to a completely uniform thickness as shown in the drawings and may have some errors.

As described above, the refractive index of the light diffusing portion structure incorporating the beads is substantially the refractive index of the beads itself, assuming that the thickness of the resin coating portion is negligible and is about 1.5 to 2.5.

And the refractive index of the lens of a single material, that is, the base film (resin, etc.), which is a molded part of the diffusion part, is about 1.3 to 1.8, so that if a single molding is performed without inserting the beads, a single base film material is used. The average radius of the lens to be shaped needs to be smaller than the average radius of the bead-type lens, and these detailed values can be adjusted by repeating additional experiments according to the design intention.

Among the structures of the optical sheet of the present invention shown in FIGS. 8, 9 and 12 to 14, the base layer 713 is disposed below the lens molding sheet 703, and the base layer 713 is, for example, a PET film. It may be made of a light-transmitting material similar to the molding portion 703 and having a surface energy similar to the surface energy of the resin that can be a material of the molding portion 703 is bonded to each other through the molding mold When used, it helps to maintain the overall strength of the optical sheet while serving as a mold or carrier.

Various members may be stacked in contact with the bottom surface of the base layer 713, for example, in contact with the light guide plate 723, which is a simple flat member as shown in FIG. 12, or on the lens portion of the diffusion sheet as shown in FIG. 13. It may be laminated (for example, as shown in FIG. 13 if the sheet is wound on a roll), or may be stacked on the prism-like protrusions of the prism sheet 733 which serves as the condenser.

In the case of all the contact (or lamination) through the bottom of the base layer, when the lower flat surface of the base layer 713 is intact, various problems may occur.

In particular, as in the case of a light guide plate, problems such as sticking as it is in contact with the plane-to-plane as it is very large or difficult to peel off occurs, and when contacting in the plane-to-point like the projection of the prism sheet or diffusion sheet Scratch occurs in the lower plane of the sheet, which may cause a problem that the transparency and flatness of the sheet are reduced.

In order to prevent the above phenomenon, as shown in FIGS. 8, 9, 11 and 14, a small protrusion 711 (which may be formed of the base sheet itself or bead inserted therein) may be additionally formed on the bottom surface of the base sheet. The operation of forming the micro-projections or the back-coating projections is called back-coating and the surface on which the projections 711 are arranged is called a back-coating surface.

Although the back coating protrusion 711 is illustrated in the figure as a convex lens shape inherent with beads, it can be molded into a concave lens shape as needed and can be used for a single material or bead.

The back coating protrusion 711 of the back coating surface (the lower surface of the reference numeral 713) is generally in the same range as the size of 1 ~ 20㎛, i.e., the size of the sub-micro lens of the present invention, the arrangement density is very low As a result, the deviation of the batch interval is also set in various ways. Because the back-coated surface does not stick to the laminated sheet or the light guide plate of the optical sheet, the contact area is reduced so that the contact surfaces slide well, and only a minimum number is required to prevent scratches on the surface of the base sheet. This is because it is necessary to minimize scattering (including reflection) from the lower side of the unintentional sheet to the opposite side.

Therefore, as shown in FIGS. 8, 9, 11 and 14, the intervals, sizes, and shapes of the projections appear randomly, and the photographs photographed in detail are FIGS. 15 and 16.

15 and 16 show very irregularly arranged back coated surface projections, of which, referring to the actual shape dimensions of FIG. 16, the average diameter measurements of the three projections are approximately 14.075, 6.154, 19.26 µm, etc. It is generally included in the average diameter of 1 ~ 20㎛.

While specific embodiments of the present invention have been described in detail with reference to the drawings, the technical spirit of the present invention will not be limited to the above-described embodiments.

That is, one of ordinary skill in the art to which the present invention pertains further increases the scattering, refraction, and total reflection by arranging sub-micro lenses between the main idea and the main micro lens array space. Through the technical idea of achieving a uniform diffusion performance of the optical sheet and the back sheet surface on the opposite side of the sheet to further improve the additional properties except for the optical properties of the sheet through a variety of not included in the specification and drawings of the present invention Additional modified embodiments can be presented.

In addition, in some cases, other technical fields related to the technical field of the present invention may provide an application example to which the above embodiments are applied, but in this case, all the additional embodiments and applications described above are still uniquely possessed by the present invention. It is, of course, included in the scope of the technical idea.

The optical sheet of the present invention as described above has the following effects.

First, by greatly reducing the flat void space between the main scattering lens unit to suppress the simple transmission or simple refraction as much as possible, it is possible to greatly improve the homogeneity of the light, that is, the haze (haze), and thus the diffusion sheet and the light collecting sheet having multiple beads Satisfactory brightness and haze can be achieved without stacking a large number.

Second, due to the increase in the optical interface through a micro lens of a smaller size than the main scattering lens, it exhibits an excellent light diffusion effect while minimizing the number of sheets stacked.

Third, micro projections may be formed on the lower surface of the sheet within a range that does not significantly degrade the overall optical properties of the sheet, thereby greatly improving the mechanical properties of the sheet and handling in manufacturing, transport, and storage.

Claims (17)

A main micro lens and a sub micro lens arranged on the same optical surface and scattering light, The main micro lens is arranged in a grid, The sub-micro lenses are arranged at an approximately center position inside the closed polygon formed by connecting the vertices of the grating and the center points of the main micro lenses, and intersected with each other. The length of the sum of the average diameter of the sub-micro lens and the average diameter of the main micro lens is less than the average diagonal length or average height of the closed polygon. The method of claim 1, The length of the sum of the average diameter of the sub-micro lens and the average diameter of the main micro lens is greater than the average diameter of the closed polygon divided by the number of vertices of the closed polygon. The method of claim 1, And the average diameter of the sub microlenses is greater than the minimum distance between the main microlenses. The method of claim 1, And an average height on the optical surface of the sub micro lens is smaller than an average height on the optical surface of the main micro lens. A unit grid type light diffusion surface on which main microlenses for scattering light are arranged; At least one sub-micro lens disposed on the light diffusion surface; A sub-micro lens in which the light diffusion surfaces are arranged adjacent to each other, and at least one sub-lens disposed on adjacent unit linear boundary lines; Including but not limited to: The average diameter of the sub-micro lens is larger than the average length of the one side of the grating minus the average diameter of the main micro lens. The method of claim 5, The average diameter of the sub-micro lens is smaller than the minimum side length of the grating. The method of claim 5, And the average diameter of the sub microlenses is smaller than the minimum diagonal length of the grating minus the average diameter of the main microlenses. The method of claim 5, And the light scattering center of the main microlens is higher than the uppermost end of the submicrolens so that light scattered from the main microlens is not reincident to the submicrolens. The method according to claim 1 or 5, The micro lens is formed of the same material as the optical sheet or optical sheet, characterized in that formed by inserting a bead (bead) having a larger refractive index than the optical sheet. The method of claim 9, When the microlens is formed of the same material as the optical sheet, the average diameter of the microlens is equal to the refractive index of the bead so as to have the same scattering effect as that formed by inserting a bead having a larger refractive index than the optical sheet material. The optical sheet, characterized in that to form smaller than the amount corresponding to. The method according to claim 1 or 5, And a back coating surface randomly arranged at a lower density than the array density of the sub-microlenses on the opposite plane of the optical sheet, and having a back coating surface having micro projections smaller than the size of the sub-microlenses. The method of claim 11, The size of the micro-projections or the sub-micro lens is selected in the range of about 1 ~ 20㎛, wherein the size deviation of the micro-projections is larger than the size deviation of the sub-micro lens. Hemispherical first and second optical elements arranged on the same optical line and scattering light; The first optical device and the second optical device are alternately arranged alternately to form a single optical line, And an optical surface arranged such that the second optical element of another optical line is positioned next to a point where the first optical element of one optical line is positioned to form one optical surface by continuously arranging the optical lines. The method of claim 13, And the size of the second optical element is smaller than the size of the first optical element and larger than the minimum adjacent distance between the first optical elements on the optical surface. The method of claim 13, The optical element is formed of the same material as the light diffusion surface or is formed by inserting a bead (bead) having a larger refractive index than the light diffusion surface. The method of claim 15, When the optical device is formed of the same material as the optical sheet, the average size of the optical device may be equal to the scattering effect of the optical device. The optical sheet, characterized in that formed smaller than the amount corresponding to the refractive index. The method of claim 14, On the opposite side of the optical surface is an optical sheet, characterized in that the back coating surface is further formed randomly arranged at intervals wider than the spacing of the second optical element smaller than the size of the second optical element.

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