JP6550992B2 - Quantum dot sheet, backlight and liquid crystal display - Google Patents

Description

  The present invention relates to a quantum dot sheet, a backlight, and a liquid crystal display.

  Developments for improving the light emission efficiency and color rendering of liquid crystal display backlights and lighting devices are advancing. In recent years, in order to realize such a light emitting device, a combination of a light source (a blue LED or the like that emits blue light) generating primary light and a quantum dot phosphor (hereinafter referred to as "quantum dot") made of semiconductor fine particles Light emitting devices have been developed.

The quantum dot is, for example, a nano-sized compound semiconductor fine particle constituted of a semiconductor fine particle constituted of a core of CdSe and a shell of ZnS, and a ligand covering the periphery of the shell. The quantum dot has a quantum confinement effect because its particle size is smaller than the Bohr radius of the compound semiconductor exciton. Therefore, the luminous efficiency of the quantum dots is higher than that of a phosphor (rare earth phosphor) that uses a rare earth ion as a conventional activator, and a high luminous efficiency of 90% or more can be realized.
In addition, since the emission wavelength of the quantum dot is determined by the band gap energy of the compound semiconductor fine particle thus quantized, it is necessary to obtain an arbitrary emission wavelength, that is, an arbitrary emission spectrum, by changing the particle diameter of the quantum dot. Can do. By combining these quantum dots with a blue LED or the like, it is possible to realize a backlight with high luminous efficiency and high color rendering (see, for example, Patent Documents 1 to 3).

As a method of incorporating quantum dots into a backlight device, an on-chip method of incorporating quantum dots into a light source, an on-edge method of disposing a transparent tube containing quantum dots between a light source and a light guide plate, and the light output side of a light guide plate There is known an on-surface method in which a sheet (quantum dot sheet) including quantum dots is disposed on a light source or a light source.
However, in the on-chip method, since the quantum dot is incorporated in the light source, the quantum dot is exposed to a high temperature, and the conversion efficiency of the quantum dot is degraded. Further, in the on-edge method, since the transparent tube accommodating the quantum dots is disposed between the light source and the light guide plate, the size becomes large. In particular, in mobile devices, since miniaturization is required, it is difficult to cope with the on-edge method.
On the other hand, in the on-surface method, there is no problem as described above, and it is possible to use a conventionally used backlight device. For these reasons, it is currently being studied to incorporate quantum dots into a backlight device by an on-surface method.

  However, an on-surface type backlight using a quantum dot sheet sometimes has a tint that does not turn white at the edge region, and the tint may change depending on the viewing direction.

International Publication No. 2012/132239 JP, 2015-18131, A Japanese Patent Laying-Open No. 2015-28139

  In view of the above problems, an object of the present invention is to provide a quantum dot sheet, a backlight, and a liquid crystal display device in which the color of an edge region and the angle dependency of the color are improved.

The present inventors have intensively studied to solve the above-mentioned problems. As a result, it has been found that the cause of the above problem is that the primary light has directivity while the secondary light emitted from the quantum dot does not have directivity, and this has been solved.
That is, the present invention provides the following quantum dot sheets, backlights, and liquid crystal display devices of [1] to [11].

[1] A quantum dot sheet, wherein the quantum dot sheet has a quantum dot containing layer including a quantum dot that absorbs primary light and emits secondary light and a binder resin, and is any one of the quantum dot sheets When the visible light with a halogen lamp (12 V, 48 W) as the light source is vertically irradiated to one surface and the intensity of the transmitted light is measured every one degree in the range of -85 degrees to +85 degrees, A quantum dot sheet that satisfies at least one of the following conditions A-1 and B-1.
<Condition A-1>
The sum of the intensity of the maximum value of the intensity of the transmitted light of -85 degrees to + 85 degrees to 1 and normalized -30 degrees to + 30 degrees when upon the _{P 30, P 30} is more than 50.
<Condition B-1>
The absolute value of α is 30 degrees or more, where α is the diffusion angle indicating the intensity half of the maximum value.
[2] The quantum dot sheet according to the above [1], further satisfying the following condition A-2.
<Condition A-2>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -45 degrees to + 45 degrees when upon the _{P 45, P 45} is more than 60.
[3] The quantum dot sheet according to [1] or [2], which further satisfies the following condition A-3.
<Condition A-3>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -60 degrees to + 60 degrees when upon the _{P 60, P 60} is more than 75.
[4] The quantum dot sheet according to any one of [1] to [3], further satisfying the following condition B-2.
<Condition B-2>
The absolute value of β is 45 degrees or more, where β is the diffusion angle indicating the intensity of 1/3 of the maximum value.

[5] The quantum dot sheet according to any one of the above [1] to [4], which contains internal diffusion particles in the quantum dot-containing layer.
[6] When the refractive index of the binder resin is n _A and the refractive index of the internal diffusion particles is n _B , the n _B / n _A is 1.02 or more or 0.98 or less [5] The quantum dot sheet described in 1.
[7] The quantum dot sheet according to any one of [1] to [6], wherein both sides of the quantum dot-containing layer are sandwiched between light-transmitting substrates.
[8] The quantum dot sheet according to any one of [1] to [7], further including a light diffusion layer.
[9] The at least one surface of the quantum dot sheet has an arithmetic average roughness Ra of 0.1 to 10 μm according to JIS B 0601: 2001, and a cutoff value of 0.8 mm according to the above [1] to [8] The quantum dot sheet in any one.
[10] At least one light source for emitting primary light, an optical plate disposed adjacent to the light source, for guiding light or diffusion, and a quantum dot sheet disposed on the light emitting side of the optical plate Back light provided with the said quantum dot sheet | seat is a quantum dot sheet in any one of said [1]-[9].
[11] A liquid crystal display device comprising a backlight and a liquid crystal panel, wherein the backlight is the backlight according to the above [10].

  The quantum dot sheet, backlight, and liquid crystal display device of the present invention can improve the color of the edge region and the angle dependency of the color.

It is a sectional view showing one embodiment of a quantum dot sheet of the present invention. It is sectional drawing which shows other embodiment of the quantum dot sheet | seat of this invention. It is sectional drawing which shows other embodiment of the quantum dot sheet | seat of this invention. It is a sectional view showing one embodiment of a back light of the present invention. It is sectional drawing which shows other embodiment of the backlight of this invention. FIG. 1 is a cross-sectional view showing an embodiment of a liquid crystal display device of the present invention. FIG. 2 is a view showing intensity distribution of transmitted light of the quantum dot sheet of Example 1. FIG. 18 is a view showing intensity distribution of transmitted light of the quantum dot sheet of Example 3. It is a figure which shows intensity distribution of the transmitted light of the quantum dot sheet | seat of the comparative example 1. FIG.

Hereinafter, embodiments of the present invention will be described.
[Quantum dot sheet]
The quantum dot sheet of the present invention is a quantum dot sheet, and the quantum dot sheet has a quantum dot containing layer including a quantum dot that absorbs primary light and emits secondary light, and a binder resin, Visible light with a halogen lamp (12V, 48W) as the light source is irradiated vertically on one of the surfaces of the dot sheet, and the intensity of transmitted light is in the range of -85 degrees to +85 degrees every 1 degree. At the time of measurement, at least one of the following condition A-1 and condition B-1 is satisfied.
<Condition A-1>
The sum of the intensity of the maximum value of the intensity of the transmitted light of -85 degrees to + 85 degrees to 1 and normalized -30 degrees to + 30 degrees when upon the _{P 30, P 30} is more than 50.
<Condition B-1>
The absolute value of α is equal to or greater than 30 degrees, where α is a diffusion angle showing an intensity half of the maximum value.

Condition A-1
Condition A-1 is, P ₃₀ indicating the sum of intensities of up to -30 degrees to + 30 degrees at the time of 1 and the normalized maximum value of the intensity of the transmitted light is required to be 50 or more.
Hereinafter, the reason why the color dependency of the edge area and the angular dependency of the color tint can be improved by satisfying the condition A-1 will be described.

First, the color of the edge area and the cause of the color unevenness in the surface will be described.
The secondary light emitted from the quantum dots diffuses evenly at 360 degrees. On the other hand, the primary light has directivity and the diffusion direction is not uniform. Further, among the primary light, those which are transmitted without being absorbed by the quantum dots also have directivity and the diffusion direction is not uniform.
Therefore, when primary light is incident on a quantum dot sheet formed simply by forming a quantum dot-containing layer, secondary light of the transmitted light is uniform diffusion, while primary light has directivity. . The secondary light, which is evenly diffused, diffuses a large proportion of light up to a high angle, and light tends to leak from the edge region of the quantum dot sheet, while the primary light has a small proportion of diffused light at a high angle, and the edge Light does not leak easily from the area. For this reason, the ratio of primary light increases in the edge area, and the tint of the primary light (or bluish if the primary light is blue) is obtained.
Further, when primary light has directivity, the amount of primary light is sufficient in the low angle region, while the amount of primary light is reduced in the high angle region. For this reason, the tint is different between the low angle region and the high angle region, resulting in an angle dependency of the tint.
Thus, it is considered that the color and the angular dependence of the color of the edge area are caused by the directivity of the primary light.

Next, the meaning of the condition A-1 will be described.
The intensity of the transmitted light is usually the largest in the regular transmission direction (0 degree), and decreases as the angle increases in the positive and negative directions. The degree to which the intensity of the transmitted light decreases as the angle increases in the positive direction and the negative direction increases as the diffusion decreases. This tendency is the same as when the maximum value of the intensity of transmitted light is normalized to 1.
Therefore, the maximum value of the intensity of transmitted light is normalized to 1, and P ₃₀ which is the sum of the intensities from −30 degrees to +30 degrees when normalized indicates the intensity of diffusion of the sample in the stable field of view. It will be. The stable visual field is a range in which information can be accepted without difficulty by effective visual field + head movement, and the horizontal direction is ± 30 to 45 degrees, the upward direction is 20 to 30 degrees, and the downward direction is 25 to 40 degrees. (E.g., the Internet <URL: http://dbnst.nii.ac.jp/view_image/2515/4526? Height = 785 & width = 421>). That is, P ₃₀ indicates the diffusion intensity in the minimum necessary range of the stable focus. Since the intensity in the normal transmission direction (0 degree) varies greatly depending on the type of sample and light source, even if the measured values of -30 degrees to +30 degrees are summed as they are, the sum is used for comparison of the intensity of diffusion. I do not connect.
Further, the ratio of the primary light is small in the high angle region, while the ratio of the primary light is large in the low angle region. Therefore, it is considered that the sum of the intensities in the angular range excluding the high angle appropriately represents the intensity of the first-order light diffusion.
Therefore, satisfying the condition A-1 (P ₃₀ is 50 or more) means that the quantum dot sheet is strongly diffused and the primary light is strongly diffused in the minimum necessary range of the stable focus. Yes.
And directivity can be brought close to equalization by strong diffusion. For this reason, by satisfying the condition A-1 (P ₃₀ is 50 or more), it is considered that the color and the angular dependence of the color of the edge area due to the directivity of the primary light can be improved.
On the other hand, when the condition A-1 is not satisfied, it is considered that the directivity of the primary light cannot be sufficiently uniformed, and the color of the edge region and the angle dependency of the color cannot be improved.

P ₃₀ is preferably 53 or more, more preferably 55 or more, from the viewpoint of further improving the color of the edge area and the angular dependence of the color. In addition, it is preferable that _P30 is 60 or less from a viewpoint of preventing the light leak of a polarizing plate.

Condition B-1
Condition B-1 requires that the absolute value of α be 30 degrees or more, where α is a diffusion angle that indicates half of the maximum value of the intensity of transmitted light from -85 degrees to +85 degrees. doing.
Hereinafter, the reason why the color dependency of the edge area and the angular dependency of the color tint can be improved by satisfying the condition B-1 will be described.

As described above, the intensity of transmitted light is usually the largest in the normal transmission direction (0 degrees), and decreases as the angle increases in the positive and negative directions. The degree to which the intensity of the transmitted light decreases as the angle increases in the positive direction and the negative direction increases as the diffusion decreases. In other words, if the diffusion becomes strong, the intensity of the transmitted light hardly decreases even if the angle increases in the positive direction and the negative direction. Therefore, the angle α indicating the intensity of ½ of the maximum value of the intensity of transmitted light indicates the intensity of diffusion.
Further, if it is assumed that the diffusion has a predetermined intensity, no difference in intensity is recognized by the human eye in the range of the maximum value of transmitted light intensity to half the maximum value. Also, as described above, the ratio of primary light is high in the low angle region. Therefore, that the absolute value of α is 30 degrees or more and the condition B-1 is satisfied is that the diffusion is strong to such an extent that the intensity difference is hard to be recognized within the minimum necessary range of the stable fixation. It means that diffusion is strong.
Then, as described above, although the color of the edge area and the angular dependency of the color are considered to be caused by the directivity of the primary light, the directivity can be brought closer to uniformization by strong diffusion.
For this reason, it is considered that by satisfying the condition B-1 (the absolute value of α is 30 degrees or more), the color of the edge region caused by the directivity of the primary light and the angle dependency of the color can be improved.
On the other hand, when the condition B-1 is not satisfied, it is considered that the directivity of the primary light cannot be made sufficiently uniform, and the color of the edge region and the angle dependency of the color cannot be improved.

  The absolute value of α is preferably 40 degrees or more, more preferably 50 degrees or more, and more preferably 55 degrees or more, from the viewpoint of further improving the color of the edge area and the angle dependency of the color. Is more preferred. In addition, from the viewpoint of preventing light leakage from the polarizing plate, the absolute value of α is preferably 60 degrees or less.

α can be calculated on the basis of an intensity distribution diagram created by an approximate curve by linear interpolation of intensity values for each degree and the maximum value of the intensity of transmitted light. The same applies to β described later.
In addition, the angle which shows 1/2 of the maximum value of the intensity | strength of transmitted light exists in a plus direction and a minus direction, respectively. In the present invention, the absolute value of α means the average value of the absolute values in the positive and negative directions. The same applies to β described later.

  From the above, by satisfying Condition A-1 or Condition B-1, the color of the edge region and the angle dependency of the color can be improved. In addition, it is preferable to satisfy | fill condition A-1 and condition B-1 from a viewpoint of improving the color dependency of an edge area | region, and the angle dependency of a hue.

Further, the quantum dot sheet of the present invention preferably further satisfies the following condition A-2.
<Condition A-2>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -45 degrees to + 45 degrees when upon the _{P 45, P 45} is more than 60.

Meeting the condition A-2 means that the diffusion is strong in the entire range of the stable fixation field. Therefore, when the condition A-2 is satisfied, the color of the edge region and the angle dependency of the color can be further improved.
P ₄₅ is more preferably 70 or more, and still more preferably 75 or more. In addition, it is preferable that _P45 is 85 or less from a viewpoint of preventing the light leakage of a polarizing plate.

Further, the quantum dot sheet of the present invention preferably further satisfies the following condition A-3.
<Condition A-3>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -60 degrees to + 60 degrees when upon the _{P 60, P 60} is more than 75.

The position where the viewer can easily see the screen of the display device is the position facing the screen. However, since the portable information terminal is held by hand, it often deviates from the position where it faces. In addition, when a plurality of people visually recognize the screen, persons positioned at both left and right sides visually recognize the screen from diagonal directions. In such a case, the angle formed by the viewer's line of sight and the edge of the screen may be about 60 degrees.
Satisfying the condition A-3 means that the diffusion is strong even in the high-angle region as described above. Therefore, when the condition A-3 is satisfied, the color of the edge region and the angle dependency of the color can be further improved.
P ₆₀ is more preferably 83 or more, still more preferably 90 or more. In addition, it is preferable that _P60 is 105 or less from a viewpoint of preventing the light leak of a polarizing plate.

Moreover, it is preferable that the quantum dot sheet of the present invention further satisfies the following condition A-4.
<Condition A-4>
P ₄₅ -P ₃₀ is 13 or more.

That P ₄₅ -P ₃₀ is 13 or more means that the diffusion is not sharply weakened between 30 degrees and 45 degrees. Therefore, when the condition A-4 is satisfied, the color of the edge region and the angle dependency of the color can be further improved.
P ₄₅ -P ₃₀ is more preferably 15 or more, and further preferably 20 or more. From the viewpoint of preventing light leakage of the polarizing plate, P ₄₅ -P ₃₀ is preferably 25 or less.

Further, the quantum dot sheet of the present invention preferably further satisfies the following condition A-5.
<Condition A-5>
P ₆₀ -P ₄₅ is 8 or more.

The fact that P ₆₀ -P ₄₅ is 8 or more means that the diffusion is not rapidly weakened between 45 degrees and 60 degrees. Therefore, when the condition A-5 is satisfied, the color of the edge region and the angle dependency of the color can be further improved.
P ₆₀ -P ₄₅ is more preferably 12 or more, further preferably 15 or more. From the viewpoint of preventing light leakage of polarizing _plates, P 60 _{-P 45} is preferably 20 or less.

Further, the quantum dot sheet of the present invention preferably further satisfies the following condition B-2.
<Condition B-2>
The absolute value of β is 45 degrees or more, where β is a diffusion angle indicating the intensity of 1/3 of the maximum intensity of transmitted light of −85 degrees to +85 degrees.

Usually, the maximum value of the intensity of the transmitted light is in the regular transmission direction (0 degree). Also, even if the diffusion has a certain intensity, the maximum intensity of the transmitted light and the intensity one third of the maximum value are within the range recognized as the intensity difference of the human eye (however, But not painful). In addition, as described above, the maximum angle of the stable fixation field is 45 degrees. Further, the ratio of primary light is large in a low to medium angle region within ± 45 degrees. That is, when the absolute value of β is 45 degrees or more and the condition B-2 is satisfied, the diffusion is strong to the extent that the range recognized as the intensity difference by the human eye is outside the range of the stable focus field, and the primary It means that the diffusion to light is strong.
Therefore, by satisfying the condition B-2, the color of the edge region and the angle dependency of the color can be further improved.
The absolute value of β is more preferably 58 degrees or more, further preferably 65 degrees or more. From the viewpoint of preventing light leakage of the polarizing plate, the absolute value of β is preferably 75 degrees or less.

Further, the quantum dot sheet of the present invention preferably further satisfies the following condition B-3.
<Condition B-3>
The difference between the absolute value of β and the absolute value of α is 11.5 degrees or more.

The difference between the absolute value of β and the absolute value of α is not less than 11.5 degrees between the angle indicating the intensity of 1/2 of the maximum value and the angle indicating the intensity of 1/3 of the maximum value. This means that diffusion does not suddenly weaken. Therefore, when the condition B-3 is satisfied, the color of the edge region and the angle dependency of the color can be further improved.
The difference between the absolute value of β and the absolute value of α is more preferably 12 degrees or more. From the viewpoint of preventing light leakage of the polarizing plate, the difference between the absolute value of β and the absolute value of α is preferably 15 degrees or less.

Method of measuring transmitted light intensity The intensity of transmitted light can be measured as follows.
First, visible light with a halogen lamp (12 V, 48 W) as a light source is irradiated as parallel light onto one of the surfaces of the quantum dot sheet. In the measurement of the intensity of transmitted light, the surface on which the quantum dot sheet is irradiated with light is the light incident surface when the quantum dot sheet is used as a backlight (the surface facing the optical plate for light guiding or diffusion) It is preferable to
After irradiating the light, the transmitted light is scanned by the light receiver at every angle in a certain angle range, and the intensity (luminance) at each angle is measured. The measurement range is a measurement in a range of ± 85 degrees, where the vertical direction is 0 degrees (regular transmission direction). At the time of intensity measurement, the brightness of the light source is made constant. When measuring the intensity (luminous intensity), the aperture angle of the light receiver detected by the diaphragm of the light receiver is set to 1 degree. Therefore, for example, in the measurement of 0 degree (the regular transmission direction), the range of ± 0.5 degrees is measured, and in the measurement of 1 degree, the range of 0.5 to 1.5 degrees is measured, and the measurement of −1 degree In this case, the range of -0.5 to -1.5 degrees is to be measured. There is no restriction | limiting in particular about the apparatus which measures intensity | strength, A general purpose goniophotometer (goniophotometer) can be used. In the present invention, as a variable angle photometer, a trade name GC5000L (beam diameter: about 3 mm, inclination angle within the beam: within 0.8 degree, aperture angle of the receiver: 1 degree) manufactured by Nippon Denshoku Kogyo Co., Ltd. is used. did.
FIGS. 7-9 is a figure which shows the intensity distribution which normalized the transmitted light of the quantum dot sheet | seat of Example 1, 3 and the comparative example 1. FIG. 7 to 9 are approximate curves obtained by linear interpolation of the intensity values for each degree.
_P 30 described _{above, P 45,} P _60, the α and beta, an average value when measured 20 times.

  As shown in FIGS. 7 to 9, in the quantum dot sheet of the present invention, the shape of the intensity distribution map of transmitted light is convex upward, and goes from the front direction (0 degree) toward the plus direction and the minus direction It is preferable that the shapes become substantially gradually decreasing.

Transmission image definition Further, the quantum dot sheet of the present invention is a transmission image definition in which the width of the optical comb of the image measuring instrument is 0.25 mm, 0.5 mm, and 1.0 mm, measured according to JIS K7374: 2007. degrees to _{C 0.25,} upon a _{C 0.5} and _{C 1.0, C 0.25,} it is preferable total _{C s} of _{C 0.5} and _{C 1.0} is less than 200%.
Usually, the transmitted image sharpness decreases as the diffusion becomes stronger and increases as the diffusion becomes weaker. In other words, it C _s is less than 200% indicates that strong diffusion.
Therefore, by setting C _s to 200% or less, it is possible to further improve the color and the angular dependence of the color of the edge region. Further, by the C _s 200% or less, the dot pattern of the light source shape and the light guide plate can easily concealed.
C _s is more preferably 120% or less, still more preferably 75% or less, and still more preferably 25% or less. Further, C 2 _S is more preferably 10% or less, and most preferably 0%.

In the quantum dot sheet of the present invention, the C _0.5 is _preferably 60.0% or less, and the C _1.0 is preferably 85.0% or less.
As described above, the transmitted image definition indicates the intensity of diffusion, but C _0.5 and C _1.0 indicate the intensity of diffusion at medium to high angles among the diffusion. That is, the fact that C _0.5 is 60.0% or less and C _1.0 is 85.0% or less indicates that medium to high angle diffusion is strong.
Therefore, when C _0.5 and C _1.0 satisfy the above conditions, it is possible to further improve the color and the angular dependence of the color of the edge region. In addition, when C _0.5 and C _2.0 satisfy the above condition, the shape of the light source and the dot pattern of the light guide plate can be easily concealed.
C _0.5 is more preferably 35.0% or less, further preferably 20.0% or less, and still more preferably 6.0% or less. C _0.5 is more preferably 3.0% or less, and most preferably 0%.
C _1.0 is more preferably 55.0% or less, still more preferably 40.0% or less, and still more preferably 15.0% or less. C _1.0 is more preferably 5.0% or less, and most preferably 0%.

In the quantum dot sheet of the present invention, the C _0.25 is preferably 55.0% or less.
As described above, although the transmitted image definition indicates the intensity of diffusion, C _0.25 indicates the intensity of low angle diffusion among the diffusions. That is, the fact that C _0.25 is 55.0% or less indicates that low angle diffusion is strong. In addition, when the quantum dot sheet causes interference unevenness, C _0.25 may increase despite strong diffusion. That is, the fact that C _0.25 is 55.0% or less indicates that low-angle diffusion is strong and that no interference unevenness occurs.
Therefore, by setting the C _0.25 55.0% or less, it is possible to further improve the angular dependence of color and tint of the edge region, the interference unevenness can be suppressed.
C _0.25 is more preferably 30.0% or less, still more preferably 15.0% or less, and still more preferably 4.0% or less. C _0.25 is more preferably 2.0% or less, and most preferably 0%. The reason for the increase in C _0.25 due to the interference unevenness is considered that the light emitted from the quantum dot is likely to cause interference unevenness because the wavelength width is narrow and the monochromaticity is strong, and the waveform changes due to the interference unevenness. It is done.
In the measurement of transmitted image clarity, the surface that irradiates light to the quantum dot sheet is the light incident surface when the quantum dot sheet is used as a constituent member of the backlight (the side facing the optical plate for light guide or diffusion) It is preferable that
In the present invention, C _0.25 , C _0.5 , C _1.0, and C _s are average values when measured 20 times.

Transmittance The total light transmittance of the quantum dot sheet of the present invention according to JIS K7361-1: 1997 is not particularly limited, but is usually about 40% or more.
In the measurement of the intensity of the total light transmittance, the surface which irradiates light to the quantum dot sheet is opposed to the light incident surface (optical plate for light guide or diffusion when the quantum dot sheet is used as a backlight) Side surface) is preferable.

Surface Roughness The quantum dot sheet of the present invention preferably has an arithmetic average roughness Ra of at least one surface of 0.1 to 10 μm, more preferably 0.2 to 8 μm, and 0.5 to 5 μm. More preferably. Moreover, it is preferable that both surfaces of a quantum dot sheet satisfy | fill the range of said Ra.
By setting Ra to 0.1 μm or more, it is possible to prevent adhesion with a member in contact with the quantum dot sheet. Examples of the member in contact with the quantum dot sheet include a prism sheet positioned on the light emission side of the quantum dot sheet, and an optical plate for light guiding or diffusion positioned on the light incident side of the quantum dot sheet. Moreover, the light leakage of a polarizing plate and the fall of front luminance can be suppressed by Ra being 10 micrometers or less.
In addition, by controlling the intensity of diffusion, from the viewpoint of balancing the suppression of the color angle dependency, the suppression of the color of the edge region, the light leakage of the polarizing plate, and the suppression of the decrease in front luminance, Ra is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm. Further, by setting the Ra on the light incident surface side to 1 μm or more, retroreflectivity is imparted, the light recycling rate is increased, and the quantum dot content can be reduced.
In addition, Ra and Rz _{JIS mentioned} later are based on JISB0601: 2001, and are the average value at the time of measuring 20 times by cutoff value 0.8 mm.

The quantum dot sheet of the present invention preferably has a ten-point average roughness Rz _{JIS of} at least one surface of 0.120 μm, more preferably 0.2 to 10 μm, and 0.5 to 8 μm. Is more preferred. Moreover, it is preferable that both surfaces of a quantum dot sheet satisfy | fill the range of the said Rz _JIS .
The fact that the Rz _JIS satisfies the above range indicates that the surface roughness of the quantum dot sheet has a certain degree of randomness and there is no extreme deviation in the roughness. Therefore, when Rz _JIS satisfy | fills the said range, while being able to reduce the bias | inclination of a spreading | diffusion, local adhesion can be prevented.
In addition, by controlling the intensity of diffusion, from the viewpoint of balancing the suppression of the color angle dependency, the suppression of the color of the edge region, the light leakage of the polarizing plate, and the suppression of the decrease in front luminance, Rz _JIS is preferably 1 to 10 μm, and more preferably 2 to 8 μm.
In order to make Ra and Rz _JIS into the above range, a light diffusion layer described later may be positioned on the outermost surface of the quantum dot sheet.

Configuration of Quantum Dot Sheet The quantum dot sheet of the present invention has a quantum dot-containing layer including a quantum dot that absorbs primary light and emits secondary light, and a binder resin.
As quantum dots, the first quantum dots that absorb primary light having a wavelength corresponding to blue and emit secondary light having a wavelength corresponding to red, and the primary light that absorbs primary light having a wavelength corresponding to blue correspond to green It is preferable that at least one second quantum dot that emits secondary light having a wavelength to be emitted is included, and it is more preferable that both the first quantum dot and the second quantum dot are included.
The primary light having a wavelength corresponding to blue preferably has a peak wavelength in the range of 380 to 480 nm, and more preferably 450 nm. The secondary light having a wavelength corresponding to green preferably has a peak wavelength in the range of 495 to 570 nm, and more preferably has a peak wavelength of 528 nm. The secondary light having a wavelength corresponding to red preferably has a peak wavelength in the range of 620 to 750 nm, and more preferably 637 nm.

FIGS. 1-3 is sectional drawing which shows embodiment of the quantum dot sheet | seat of this invention. The quantum dot sheet 100 of FIG. 1 has light transmissive substrates 21 a and 21 b and light diffusion layers 42 a and 42 b on the upper and lower surfaces of the quantum dot containing layer 10. The quantum dot sheet 100 of FIG. 2 has barrier layers 32a and 32b, light-transmitting base materials 21a and 21b, and light diffusion layers 42a and 42b on the upper and lower surfaces of the quantum dot-containing layer 10. The quantum dot sheet 100 of FIG. 3 has light-transmitting substrates 21a and 21b on the upper and lower surfaces of the quantum dot-containing layer 10, and the barrier film 30a via the adhesive layers 51a and 51b on the light-transmitting substrate. 30b, and light diffusion films 40a and 40b are provided on the barrier film via the adhesive layers 52a and 52b.
1 to 3 have configurations (light transmissive substrate, barrier layer, light diffusion layer, etc.) other than the quantum dot-containing layer, the quantum dot sheet of the present invention has at least a quantum dot-containing layer. And what is necessary is just to satisfy | fill at least any one of the said conditions A-1 and the conditions B-1, and structures (light transmissive base material, a barrier layer, a light-diffusion layer, etc.) other than a quantum dot content layer are as needed. It should just be provided.
In addition, although the quantum dot sheet | seat of FIGS. 1-3 has a quantum dot containing layer only in one layer, the quantum dot sheet may have two or more layers of quantum dot containing layers.

It is preferable that a quantum dot sheet has a vertically symmetrical structure centering | focusing on a quantum dot content layer like FIGS. By having this configuration, strain can be evenly distributed, the flatness of the quantum dot sheet can be improved, and the adhesion at the interface of the quantum dot sheet can be improved. When the flatness of the quantum dot sheet is good, it is preferable in that the uniformity of in-plane luminance can be improved.
Note that a layer configuration that is vertically symmetrical in the thickness direction means that the number of layers and the type of layers are the same up and down, and the thicknesses of the layers are substantially the same. In order to say that the thickness is substantially the same, the ratio of the thickness of the upper and lower layers in the target relationship is preferably in the range of 0.95 to 1.05, and in the range of 0.97 to 1.03. Is more preferable.
Moreover, it is preferable that the layers in a symmetrical relationship have substantially the same composition. In order to say that the compositions are substantially the same, 90% by mass or more of the components of the layer is preferably identical, more preferably 95% by mass or more is identical, and 99% by mass or more is identical Further preferred.

Quantum Dot-Containing Layer The quantum dots (first quantum dots and second quantum dots) will be described below.
Quantum dot is a semiconductor nanometer-sized particle, which has specific optical and electrical properties due to the quantum confinement effect (quantum size effect) in which electrons and excitons are confined in a small nanometer-sized crystal. It exhibits properties and is also called semiconductor nanoparticles or semiconductor nanocrystals.
The quantum dot is not particularly limited as long as it is a semiconductor nanometer-sized fine particle and a material that produces a quantum confinement effect (quantum size effect). For example, as described above, there are semiconductor fine particles whose luminescent color is controlled by its own particle size, and semiconductor fine particles having a dopant. As the quantum dots in the present invention, any of semiconductor fine particles whose emission color is controlled by their own particle size and semiconductor fine particles having a dopant can be used, and both excellent color purity can be obtained.

Quantum dots differ in emission color depending on their particle size, and, for example, in the case of a quantum dot composed of only a core made of CdSe, the particle size is 2.3 nm, 3.0 nm, 3.8 nm, 4 nm. The peak wavelengths of the fluorescence spectrum at .6 nm are 528 nm, 570 nm, 592 nm, and 637 nm. That is, the particle diameter of the quantum dot that emits secondary light with a peak wavelength of 637 nm is 4.6 nm, and the particle diameter of the quantum dot that emits secondary light with a peak wavelength of 528 nm is 2.3 nm.
The quantum dot-containing layer may contain quantum dots emitting secondary light of a wavelength corresponding to red and quantum dots other than quantum dots emitting secondary light of a wavelength corresponding to green.
The content of the quantum dots is appropriately adjusted in accordance with the thickness of the quantum dot-containing layer, the recycling rate of light in the backlight, the desired color tone, and the like. If the thickness of the quantum dot-containing layer is within the range described later, the content of the quantum dots is about 0.01 to 1.0 parts by mass with respect to 100 parts by mass of the binder resin of the quantum dot-containing layer. If the content of the quantum dots is about this level, the values of transmitted light intensity and transmitted image definition are hardly affected.

Specifically, the core material of the quantum dot includes MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS II-VI group semiconductor compounds such as HgSe and HgTe, III- such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and TiSb A semiconductor crystal containing a semiconductor compound such as a group V semiconductor compound, a group IV semiconductor such as Si, Ge and Pb, or a semiconductor can be exemplified. Alternatively, a semiconductor crystal containing a semiconductor compound containing three or more elements such as InGaP can also be used.
Further, as a quantum dot composed of semiconductor fine particles having a dopant, a semiconductor crystal obtained by doping the semiconductor compound with a cation of a rare earth metal such as Eu ³⁺ , Tb ³⁺ , Ag ⁺ , or Cu ⁺ or a cation of a transition metal is used. It can also be used.
As a material for the core of the quantum dot, a semiconductor crystal such as CdS, CdSe, CdTe, InP, InGaP is used from the viewpoint of ease of fabrication, controllability of the particle diameter to obtain light emission in the visible range, and fluorescence quantum yield. Is preferred.

The quantum dot may be composed of one type of semiconductor compound or may be composed of two or more types of semiconductor compounds, and for example, a core composed of a semiconductor compound and a shell composed of a semiconductor compound different from the core It may have a core-shell type structure.
When a core-shell type quantum dot is used, the luminous efficiency of the quantum dot can be obtained by using a material having a band gap higher than that of the semiconductor compound forming the core so that excitons are confined in the core as the semiconductor forming the shell. Can be enhanced.
Examples of the core-shell structure (core / shell) having such a bandgap relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, Examples include InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, and InGaP / ZnSSe.

The size of the quantum dot may be appropriately controlled depending on the material constituting the quantum dot so that light having a desired wavelength can be obtained. As the particle size of the quantum dot decreases, the energy band gap increases. That is, as the crystal size decreases, the light emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the size of the quantum dot, the emission wavelength can be adjusted over the entire wavelength range of the ultraviolet region, the visible region, and the infrared region.
In general, the particle size (diameter) of the quantum dots is preferably in the range of 0.5 to 20 nm, particularly preferably in the range of 1 to 10 nm. The narrower the size distribution of the quantum dots, the clearer the emission color can be obtained.
The shape of the quantum dot is not particularly limited, and may be, for example, a spherical shape, a rod shape, a disk shape, or another shape. When the particle dot is not spherical, the particle size of the quantum dot can be a true spherical value having the same volume.
The quantum dot may be coated with a resin. Further, the refractive index of the binder resin of the quantum dot containing layer and n _A, the refractive index of the resin (coating resin) for covering the quantum dots upon the n _B, n _{B /} n _A is 1.02 or more, or 0 It is preferable to satisfy a relationship of .98 or less. A quantum dot coated with a resin can improve the durability of the quantum dot. In addition, when the refractive index of the binder resin and the refractive index of the coating resin satisfy the above-described relationship, the quantum dots coated with the resin exhibit the function of internal diffusion particles described later.
In the present invention, the refractive index is assumed to be light of wavelength 450 nm.

  Information such as the particle size, shape, and dispersion state of the quantum dots can be obtained by a transmission electron microscope (TEM). The crystal structure and particle size of the quantum dots can be obtained by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle size and surface of a quantum dot can also be obtained by an ultraviolet-visible (UV-Vis) absorption spectrum.

  Examples of the binder resin for the quantum dot-containing layer include thermoplastic resins, cured products of thermosetting resin compositions, and cured products of ionizing radiation curable resin compositions. Among these, from the viewpoint of durability, a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition are preferable, and a cured product of an ionizing radiation curable resin composition is more preferable.

The thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that is cured by heating.
Examples of the thermosetting resin include acrylic resin, urethane resin, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. In the thermosetting resin composition, a curing agent is added to these curable resins as necessary.

The ionizing radiation curable resin composition is a composition containing a compound having an ionizing radiation curable functional group (hereinafter also referred to as "ionizing radiation curable compound"). Examples of the ionizing radiation curable functional group include ethylenic unsaturated bond groups such as (meth) acryloyl group, vinyl group and allyl group, epoxy group, oxetanyl group and the like, among which ethylenic unsaturated bond group is preferable. . Further, among the ethylenically unsaturated bond groups, a (meth) acrylate group is preferable. Hereinafter, an ionizing radiation curable compound having a (meth) acryloyl group is referred to as a (meth) acrylate compound.
In the present specification, "(meth) acrylate" refers to methacrylate and acrylate. In the present specification, “ionizing radiation” means an electromagnetic wave or charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules, and usually ultraviolet (UV) or electron beam (EB) is used. Although it is used, other than this, charged particle beams such as electromagnetic waves such as X-rays and γ-rays, α-rays and ion beams can also be used.

The ionizing radiation curable compound may be a monofunctional ionizing radiation curable compound having only one of the above functional groups, or may be a polyfunctional ionizing radiation curable compound having two or more of the above functional groups. And mixtures thereof.
The ionizing radiation curable compound may be a monomer, an oligomer, a low molecular weight polymer, or a mixture thereof.
Among the ionizing radiation curable compounds, the monofunctional monomer is preferable in terms of improving adhesion between the quantum dot-containing layer and the light-transmitting substrate and suppressing polymerization shrinkage. In particular, when the thickness of the quantum dot-containing layer is large, the above-mentioned effect in the case of using a monofunctional monomer becomes remarkable.
Moreover, when the adhesiveness of a quantum dot content layer improves using a monofunctional monomer, it will become possible to adhere members, such as a light-transmitting base material, to a quantum dot content layer, without going through an adhesive bond layer. That is, by improving the adhesion of the quantum dot-containing layer using a monofunctional monomer, the structure of the quantum dot sheet can be easily made vertically symmetrical in the thickness direction centering on the quantum dot-containing layer. Further, the moisture resistance and the oxygen resistance of the quantum dot can be improved by bringing the quantum dot-containing layer into close contact with a member such as a light transmitting substrate without interposing the adhesive layer.
The proportion of the monofunctional monomer in the total ionizing radiation curable compound is preferably 40% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, and 90% by mass. It is further more preferable that it is the above, and it is most preferable that it is 100 mass%.

  In addition, since the quantum dots are vulnerable to humidity, it is preferable to use as the main component an ionizing radiation curable compound that does not have a hydroxyl group in the molecule. Specifically, the ratio of the ionizing radiation curable compound having no hydroxyl group in the molecule to the total ionizing radiation curable compound is preferably 80% by mass or more, more preferably 90% by mass or more, and 100 More preferably, it is mass%.

  Examples of ionizing radiation curable compounds that do not contain a hydroxyl group in the molecule include ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate, octyl (meth) acrylate, dicyclopentenyl ( Monofunctional (meth) acrylate compounds such as (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,6-hexanediol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) Acrylate, tricyclodecanedimethanol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxy tri (meth) acrylate, dipentaerythritol hexene (Meth) acrylate, pentaerythritol ethoxy tetra (meth) acrylate, polyfunctional (meth) acrylate compounds such as ditrimethylolpropane tetra (meth) acrylate.

  The ionizing radiation curable compound preferably has a total carbon number of 8 or more from the viewpoint of enhancing the hydrophobicity to improve the moisture resistance of the quantum dot. In consideration of the adhesion of the quantum dot-containing layer in addition to the moisture resistance, the total number of carbon atoms of the ionizing radiation curable compound is more preferably 8-20. For example, as a monofunctional (meth) acrylate monomer having 8 or more carbon atoms in total, ethylhexyl (meth) acrylate, octyl (meth) acrylate and the like can be mentioned.

The molecular weight of the ionizing radiation curable compound is preferably 100 to 2,000, more preferably 120 to 1,000, and still more preferably 150 to 500. If the molecular weight of the ionizing radiation curable compound is 100 or more, dripping during production can be easily prevented, and if the molecular weight is 2000 or less, quantum is generated by the pressure at the time of bonding in step (d) described later. The thickness of the dot-containing layer can be easily made uniform.
When a monofunctional monomer is used as the ionizing radiation curable compound, the molecular weight of the monofunctional monomer is 100 from the viewpoint of preventing dripping at the time of production, uniforming the thickness of the quantum dot-containing layer, and adhesion of the quantum dot-containing layer. It is preferable that it is -500, It is more preferable that it is 120-400, It is further more preferable that it is 150-250.

When the ionizing radiation curable compound is an ultraviolet curable compound, the ionizing radiation curable composition preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, and the like.
The photopolymerization initiator preferably has a melting point of 20 ° C. or less. When the melting point is 20 ° C. or less, it can be easily dissolved at room temperature when added to the above-mentioned ionizing radiation-curable compound at the time of production.
The photopolymerization accelerator can reduce polymerization inhibition by air during curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc. One or more selected may be mentioned.

Internal Diffusion Particles Preferably, the quantum dot-containing layer contains internal diffusion particles. By including the internal diffusion particles, light can be diffused to a high angle, and the above-described conditions A-1 and B-1 can be easily satisfied.

As the internal diffusion particles, either organic particles or inorganic particles can be used. Examples of the organic particles include particles made of polymethyl methacrylate, acrylic-styrene copolymer, melamine resin, polycarbonate, polystyrene, polyvinyl chloride, benzoguanamine-melamine-formaldehyde condensate, silicone resin, fluorine resin, polyester, and the like. . Examples of the inorganic fine particles include fine particles made of silica, alumina, zirconia, titania and the like.
Examples of the shape of the internal diffusion particles include a spherical shape, a disk shape, a rugby ball shape, and an indefinite shape.
The internal diffusion particles may be hollow particles, porous particles, or solid particles.

Also, when the refractive index of the binder resin is n _A and the refractive index of the inner diffusion particles is n _B , the inner diffusion particles use those in which n _B / n _A is 1.02 or more or 0.98 or less It is preferable. n _B / n _A is a relative refractive index between the binder resin and the internal diffusion particles, and by making n _B / n _A 1.02 or more or 0.98 or less, light is diffused to a high angle, The conditions A-1 and B-1 described above can be easily satisfied. In addition, by setting n _B / n _A at 1.02 or more or 0.98 or less, the probability that primary light collides with the quantum dot can be increased, and the amount of use of the quantum dot can be reduced. In addition, a refractive index shall be based on the light of wavelength 450nm.
n _B / n _A is more preferably 1.10 or more and 0.95 or less, or 1.15 or more and 0.90 or less from the viewpoint of a balance between strong diffusibility and suppression of light leakage of the polarizing plate.
The refractive index of the internal diffusion particles can be measured by the Becke method, and the refractive index of the binder resin can be measured by the Abbe method.

  The content of the internal diffusion particles is preferably 1 to 40 parts by mass, and more preferably 3 to 30 parts by mass, with respect to 100 parts by mass of the binder resin. By setting the content of the internal diffusion particles in the above range, light can be diffused to a high angle while light leakage of the polarizing plate can be prevented.

  The average particle diameter of the internal diffusion particles is preferably 10 μm or less, and more preferably 3 μm or less, from the viewpoint of increasing the number of particles per content to achieve uniform diffusion. The lower limit of the average particle size of the internal diffusion particles is about 0.1 μm.

The average particle diameter of the internal diffusion particles can be calculated by the following operations (1) to (3).
(1) The transmission observation image of a quantum dot content layer is picturized with an optical microscope. The magnification is preferably 500 to 2000 times.
(2) Arbitrary 10 particles are extracted from the observation image, the long diameter and the short diameter of each particle are measured, and the particle diameter of each particle is calculated from the average of the long diameter and the short diameter. The major axis is the longest diameter on the screen of individual particles. The minor axis is a distance between two points where a line segment perpendicular to the midpoint of the line segment constituting the major axis is drawn and the perpendicular line segment intersects the particle.
(3) The same operation is performed five times on the observation image of another screen of the same sample, and the value obtained from the number average of the particle sizes of 50 particles in total is taken as the average particle size of the internal diffusion particles.
The average particle diameter of the diffusing particles in the light diffusing layer to be described later can also be calculated according to the above work.

The thickness of the quantum dot-containing layer is preferably 10 to 200 μm, more preferably 20 to 150 μm, and still more preferably 30 to 130 μm. If the thickness of the quantum dot-containing layer is in this range, it is suitable for reducing the weight and thickness of the display device, and it is possible to suppress color unevenness due to fluctuations in the thickness of the quantum dot-containing layer (manufacturing tolerance).
The thickness of the quantum dot-containing layer can be calculated, for example, by measuring the thickness at 20 locations from the image of the cross section taken using a scanning transmission electron microscope (STEM) and calculating the average value of the values at 20 locations. The STEM acceleration voltage is preferably 10 kv to 30 kV, and the magnification is preferably 1000 to 7000 times.
The thickness of the other layers constituting the quantum dot sheet can also be measured by the same method as described above. In addition, when thickness is nano order, it is preferable to make the magnification of STEM into 50,000 to 300,000 times.

Light Transmissive Substrate The quantum dot sheet of the present invention preferably has a light transmissive substrate from the viewpoint of mechanical strength and stiffness. From this point of view, it is preferable that the light-transmitting substrate has one or more sheets above and below the quantum dot-containing layer.
Moreover, it is preferable that a quantum dot sheet | seat is the structure which sandwiches both surfaces of a quantum dot content layer by a transparent substrate. According to this configuration, the quantum dot-containing layer can be protected, and the oxygen resistance and moisture resistance of the quantum dot can be improved.

The light transmitting substrate is not particularly limited, but preferably has light transmitting properties, smoothness, heat resistance, and excellent mechanical strength. Examples of such a light-transmitting substrate include polyester, triacetyl cellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyether sulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, Examples thereof include plastic films such as polyvinyl acetal, polyether ketone, acrylic, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP).
Among these, from the viewpoint of mechanical strength, dimensional stability, and heat resistance, polyester (polyethylene terephthalate, polyethylene naphthalate) that has been stretched, particularly biaxially stretched, is preferable.

The thickness of the light-transmitting substrate is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm, from the viewpoint of the balance between weather resistance, mechanical strength, handleability, and thinning.
In addition to physical treatment such as corona discharge treatment and oxidation treatment, a coating called an anchor agent or a primer may be applied to the surface of the light transmissive substrate in advance in order to improve adhesion.

Barrier Layer The quantum dot sheet of the present invention preferably has a barrier layer in order to improve the moisture resistance and oxygen resistance of the quantum dot. The barrier layer may be provided only on one side of the quantum dot-containing layer, but is preferably provided on both sides of the quantum dot-containing layer.
The barrier layer may be provided on the light transmitting substrate sandwiching the quantum dot-containing layer as shown in FIG. 2 or may be provided on another light transmitting substrate as shown in FIG.
The barrier layer is preferably provided on the side close to the quantum dot-containing layer. For example, when it has a light-diffusion layer mentioned later, it is preferable to provide a barrier layer in the quantum dot content layer side rather than a light-diffusion layer.

The barrier layer is preferably made of an inorganic substance or an inorganic oxide, and examples thereof include a vapor deposited film of an inorganic substance or an inorganic oxide, and a hydrolyzed film of an inorganic alkoxide.
The barrier layer can be formed by a known method using a known inorganic substance, inorganic oxide, inorganic alkoxide, and the like, and the composition and formation method are not particularly limited. The barrier layer may be a single layer or may have two or more layers. When two or more barrier layers are provided, each may have the same composition or a different composition.

The material of the deposited film is silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti) , Lead (Pb), zirconium (Zr), yttrium (Y), and the like, oxides thereof, and those in which an organic substance is blended.
The inorganic alkoxide which is a material of a hydrolysis film is also called metal alkoxide, and silicon alkoxides, such as tetra alkoxysilane, a titanium alkoxide, an aluminum alkoxide etc. are mentioned.

The thickness of the barrier layer is preferably 5 to 1000 nm, more preferably 7 to 700 nm, and more preferably 10 to 500 nm, from the viewpoint of the balance between moisture resistance, oxygen resistance, cracking suppression, and light transmittance. Further preferred. When the barrier layer is a deposited film, the thickness of the barrier layer is preferably 5 to 30 nm, more preferably 7 to 25 nm, and still more preferably 10 to 20 nm.
The vapor deposition film as the barrier layer may be formed, for example, by physical vapor deposition (PVD) such as vacuum deposition, sputtering or ion plating, or plasma chemical vapor deposition, thermal chemical vapor deposition, or the like. Examples thereof include a chemical vapor deposition method (CVD method) such as a growth method and a photochemical vapor deposition method.

Light Diffusion Layer The quantum dot sheet of the present invention preferably has a light diffusion layer in order to intensify the diffusion to facilitate at least one of the condition A-1 and the condition B-1.
The light diffusion layer may be provided only on one side of the quantum dot-containing layer, but is preferably provided on both sides of the quantum dot-containing layer. Moreover, it is preferable to arrange | position a light-diffusion layer in the position which can be identified with the outermost layer of a quantum dot sheet, or the outermost layer. When the light diffusing layer is provided only on one side of the quantum dot-containing layer, the light diffusing layer is preferably disposed at the outermost layer on the light emitting surface side or at a position where it can be identified with the outermost layer.
The position that can be identified with the outermost layer is the light diffusion when a thin film (thickness of 100 nm or less) that does not substantially affect the surface unevenness of the light diffusion layer is formed on the light diffusion layer. It says the position of the layer.
The light diffusion layer may be provided on a light-transmitting base material that sandwiches the quantum dot-containing layer as shown in FIGS. 1 and 2, or may be provided on another light-transmitting base material as shown in FIG. Good.

The light diffusion layer preferably has external diffusion due to surface irregularities. By arranging the light diffusion layer at a position where the light diffusion layer can be identified with the outermost layer or the outermost layer, it is possible to prevent close contact with a member (a brightness improvement sheet or the like) in contact with the quantum dot sheet. Moreover, the low to medium angle diffusion is enhanced by the external diffusion, and the conditions A-1 and B-1 can be easily satisfied.
The light diffusion layer can be formed from, for example, a binder resin and diffusion particles.

The binder resin of the light diffusion layer includes a thermoplastic resin, a cured product of a thermosetting resin composition, and a cured product of an ionizing radiation curable resin composition. Among these, from the viewpoint of scratch resistance, a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition are preferable, and a cured product of an ionizing radiation curable resin composition is more preferable.
The thermosetting resin composition and the ionizing radiation curable resin composition may be the same as those exemplified for the quantum dot-containing layer.

The ratio of the average particle diameter of the diffusion particles to the thickness of the light diffusion layer (average particle diameter of diffusion particles / thickness of the light diffusion layer) is preferably 0.10 to 2.00, preferably 0.15 to 1 It is more preferable that it is .50, and it is further preferable that it is 0.20 to 1.00.
By setting the ratio of the average particle diameter of the diffusion particles of the light diffusion layer on the light exit surface side to the thickness of the light diffusion layer to be 0.10 or more, strong external diffusion can be imparted. Further, by setting the ratio of the average particle diameter of the diffusion particles of the light diffusion layer on the light incident surface side to the thickness of the light diffusion layer to be 0.10 or more, retroreflectivity is imparted, and the light recycling rate is increased. It is possible to reduce the content of quantum dots. Further, by setting the ratio of the average particle diameter of the diffusion particles to the thickness of the light diffusion layer to 2.00 or less, the diffusion particles can be sufficiently held in the light diffusion layer.
Moreover, from the viewpoint of easily obtaining the effect based on the above ratio, the average particle diameter of the diffusion particles of the light diffusion layer is preferably 1 to 20 μm, and more preferably 1 to 10 μm.

  As the diffusion particles, both organic particles and inorganic particles can be used, and the same particles as those exemplified as the internal diffusion particles of the quantum dot-containing layer can be used.

The thickness of the light diffusion layer is preferably 1 to 30 μm, and more preferably 3 to 20 μm, from the viewpoint of the holding power of the diffusion particles and the external diffusion property.
The diffusion particles of the light diffusion layer are preferably 10 to 200 parts by mass, more preferably 30 to 170 parts by mass, with respect to 100 parts by mass of the binder resin, from the viewpoint of the balance between the diffusibility and the coating film strength. Preferably, it is 50-150 mass parts.

Adhesive Layer In order to laminate the layers constituting the quantum dot sheet, an adhesive layer may be interposed between the layers. For example, in FIG. 3, the adhesive layer is provided between the light transmitting substrate and the barrier film, and between the barrier film and the diffusion film.
The adhesive layer can be formed from a general-purpose pressure-sensitive adhesive (pressure-sensitive adhesive), a thermosetting adhesive, or an ionizing radiation-curable adhesive.
The thickness of the adhesive layer is preferably 0.5 to 20 μm, and more preferably 1 to 10 μm, from the viewpoint of adhesion and thinning.

  The quantum dot sheet may have functional layers other than the above, such as an antireflection layer and an antistatic layer.

Although the manufacturing method of a quantum dot sheet is not specifically limited, For example, it can manufacture in order of the following (a)-(d).
(A) A step of laminating a light transmitting substrate and a layer to be positioned on one surface of the quantum dot containing layer with reference to the quantum dot containing layer to obtain a laminated body A.
(B) A step of laminating a light transmitting substrate and a layer positioned on the other surface of the quantum dot containing layer with reference to the quantum dot containing layer to obtain a laminated body B.
(C) A quantum dot-containing layer coating solution containing a quantum dot that absorbs primary light and emits secondary light and a binder resin component on one surface of any one of the laminates A and B Applying and forming a quantum dot-containing layer.
(D) The process of bonding the laminated body in which the quantum dot containing layer is not formed in the step (c) and the surface on the quantum dot containing layer side of the laminated body in which the quantum dot containing layer is formed in the process (c).

  In the step (d), an adhesive layer may be used, but by bonding without using the adhesive layer, as shown in FIGS. 1 to 3, a vertically symmetrical configuration is possible centering on the quantum dot-containing layer Because it is preferable.

In the case where the binder resin of the quantum dot-containing layer is a cured product of an ionizing radiation curable resin composition, in order to bond the laminate A and the laminate B without using an adhesive layer in the step (d), It is preferable to adopt this method.
First, it is preferable that the ionizing radiation curable resin composition contains a monofunctional monomer (in other words, the quantum dot-containing layer coating liquid contains a monofunctional monomer).
Second, when forming the quantum dot-containing layer in step (c), do not irradiate ionizing radiation, or suppress the irradiation amount of ionizing radiation to leave an uncured portion in the ionizing radiation curable resin composition Alternatively, it is preferable to advance the curing of the ionizing radiation curable resin composition by irradiating it with ionizing radiation after the step (d).
Combining the first method and the second method is preferable in that the workability of bonding the two laminates without using an adhesive layer is improved in step (d).

[Backlight]
The backlight of the present invention includes at least one light source that emits primary light, an optical plate disposed adjacent to the light source, for guiding or diffusing light, and a quantum disposed on a light output side of the optical plate. In a backlight including a dot sheet, the quantum dot sheet is the above-described quantum dot sheet of the present invention.
When the conditions A-1 or B-1 are satisfied regardless of whether light is incident from any of the upper and lower surfaces of the quantum dot sheet, the direction in which the quantum dot sheet is installed in the backlight is not particularly limited. On the other hand, when the condition A-1 or the condition B-1 is satisfied only when light is incident from one of the upper and lower surfaces of the quantum dot sheet, the light incident surface at the time of satisfying the condition is a light guide or diffusion It is assumed that a quantum dot sheet is placed on the backlight so as to face the optical plate.

  As an example of the backlight of the present invention, an edge light type backlight as shown in FIG. 4 or a direct type backlight as shown in FIG. 5 can be adopted.

  The optical plate 120 used in the edge light type backlight of FIG. 4 is an optical member for guiding the primary light emitted from the light source 110, and is a so-called light guide plate. The light guide plate has, for example, a substantially flat shape formed such that at least one surface is a light incident surface and one surface substantially orthogonal to the light incident surface is a light emitting surface.

  The light guide plate is mainly made of a matrix resin selected from highly transparent resins such as polymethyl methacrylate. The light guide plate may be added with resin particles having a refractive index different from that of the matrix resin as required. Each surface of the light guide plate may have a complicated surface shape instead of a uniform plane, and may be provided with a dot pattern or the like.

  The optical plate 120 used in the direct type backlight of FIG. 5 is an optical member (light diffusing material) having light diffusibility for making the pattern of the light source 110 difficult to see. Examples of the light diffusing material include a milky white resin plate having a thickness of about 1 to 3 mm.

  In addition to the above-described light source, optical plate and quantum dot sheet, edge light type and direct type backlights may be a reflector, a light diffusion film, a prism sheet, a brightness enhancement film (BEF) and a reflection type according to the purpose. One or more members selected from a polarizing film (DBEF) and the like may be provided. The reflecting plate is disposed on the side opposite to the light emitting surface side of the optical plate. The light diffusion film, the prism sheet, the brightness enhancement film, and the reflective polarizing film are disposed on the light exit surface side of the optical plate. Providing at least one member selected from a reflection plate, a light diffusion film, a prism sheet, a brightness enhancement film, a reflective polarizing film, and the like to provide a backlight having an excellent balance of front brightness, viewing angle, etc. Can.

In the edge light type and direct type backlights, the light source 110 is a light emitter that emits primary light, and it is preferable to use a light emitter that emits primary light having a wavelength corresponding to blue. The primary light having a wavelength corresponding to blue preferably has a peak wavelength in the range of 380 to 480 nm, and more preferably 450 nm. The light source 110 is preferably an LED light source from the viewpoint of simplifying and miniaturizing a device for installing a backlight, and more preferably a blue monochromatic LED light source. The number of the light sources 110 is at least one, and a plurality of light sources 110 are preferable from the viewpoint of emitting sufficient primary light.
In addition, when only one of the first quantum dots and the second quantum dots is contained in the quantum dot-containing layer of the quantum dot sheet, in addition to the primary light source composed of a light emitter that emits primary light having a wavelength corresponding to blue. It is preferable to have an auxiliary light source. Specifically, when only the first quantum dots are contained in the quantum dot-containing layer, it is preferable to use a light emitter emitting light of a wavelength corresponding to green as an auxiliary light source. Moreover, when only the 2nd quantum dot is contained in a quantum dot content layer, it is preferable to use the light-emitting body which emits the light of the wavelength equivalent to red as an auxiliary light source.

  Since the backlight of the present invention uses the above-described quantum dot sheet of the present invention, the color of the edge region of the backlight and the angle dependency of the color can be improved.

[Liquid Crystal Display]
The liquid crystal display device of the present invention is a liquid crystal display device provided with a backlight and a liquid crystal panel, and the backlight is the above-described backlight of the present invention.

  FIG. 6 is a cross-sectional view showing an embodiment of the liquid crystal display device of the present invention. The liquid crystal display device 300 in FIG. 6 includes a backlight 200 and a liquid crystal panel 210. Further, the backlight 200 and the liquid crystal panel 210 are incorporated and fixed in the holder 220.

  The liquid crystal panel includes a polarizing plate (not shown) and a color filter (not shown). The liquid crystal panel is not particularly limited, and generally known liquid crystal panels for liquid crystal display devices can be used. For example, it is possible to use a liquid crystal panel having a general structure in which the upper and lower sides of the liquid crystal layer are sandwiched by glass plates, specifically, display panels such as TN, STN, VA, IPS and OCB.

  The polarizing plate is not particularly limited as long as it has desired polarization characteristics, and generally known polarizing plates can be used as a polarizing plate for a liquid crystal display device. Specifically, for example, a polyvinyl alcohol film is stretched, and a polarizing plate containing iodine is preferably used.

The color filter is not particularly limited. For example, a color filter that is generally known as a color filter of a liquid crystal display device can be used. The color filter is usually composed of transparent colored patterns of red, green and blue colors, each of which is composed of a resin composition in which a coloring agent is dissolved or dispersed, preferably pigment fine particles are dispersed. .
The method for forming a color filter is a method of forming an ink composition colored in a predetermined color and printing the prepared color pattern, or a photosensitive resin composition of a paint type containing a colorant of a predetermined color The method of forming by a photolithographic method using a thing is mentioned.

  The display image of the liquid crystal display device is displayed in color by passing white light emitted from the backlight through the color filter. The liquid crystal display device can realize a display that is excellent in brightness and efficiency and generates a very clear color by using a color filter that matches the spectrum of backlight by quantum dots.

  The liquid crystal panel may have a configuration in which an arbitrary layer is formed as a single layer or multiple layers on a color filter. The optional layer is not particularly limited, and, for example, a sensor layer for touch panel, hard coat layer, antistatic layer, low refractive index layer, high refractive index layer, antiglare layer, antifouling layer, antireflective layer, high dielectric A body layer, an electromagnetic wave shielding layer, an adhesive layer, etc. are mentioned.

  Since the liquid crystal display device of the present invention uses the above-described backlight of the present invention, the color of the edge region of the display image and the angle dependency of the color can be improved.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples. “Part” and “%” are based on mass unless otherwise specified. Further, the refractive index is a refractive index with a wavelength of 450 nm unless otherwise specified.

1. Physical Property Measurement and Evaluation of Quantum Dot Sheet The physical property measurement and evaluation of the quantum dot sheet of Examples and Comparative Examples were performed as follows. The results are shown in Table 1.

1-1. Intensity of transmitted light A light source angle 0 in transmission measurement using a variable angle photometer (GC-5000 L, manufactured by Nippon Denshoku Kogyo Co., Ltd., light source: halogen lamp (12 V, 48 W)) according to the method described in the specification. The sensitivity setting was set to 1000 times, the intensity of the transmitted light of the quantum dot sheet was measured every degree, and the measured intensities were normalized to calculate P ₃₀ , P ₄₅ and P ₆₀ . Moreover, an approximate curve by linear interpolation of the intensity value for each degree was created from the measurement result, and the absolute values of α and β were calculated from the approximate curve and the maximum value of the intensity of transmitted light. The average value when measured 20 times is shown in Table 1. In addition, the intensity | strength measured the range of +/- 85 degree of a regular transmission direction (0 degree).

1-2. Transmission Image Sharpness With respect to the quantum dot sheets of Examples 1 to 3, C _0.25 according to JIS K 7374: 2007 using an image clarity measuring device manufactured by Suga Test Instruments Co., Ltd. (trade name: ICM-1T). , C _0.5 and C _1.0 were measured. The average value when measured 20 times is shown in Table 1.

1-3. Surface roughness Ra and Rz on the surface of the quantum dot sheet using a surface roughness measuring instrument (model number: SE-3400 / manufactured by Kosaka Laboratory Ltd.) according to JIS B0601: 2001 under the following measurement conditions. _JIS was measured. The average value when measured 20 times is shown in Table 1.
[The stylus of the surface roughness detection unit]
Kosaka Research Institute product name SE2555N (tip radius of curvature: 2 μm, apex angle: 90 degrees, material: diamond)
[Measurement conditions of surface roughness measuring instrument]
Reference length (roughness curve cut-off value λc): 0.8 mm
-Evaluation length (reference length (cutoff value λc) x 5): 4.0 mm
・ Feeding speed of stylus: 0.5 mm / s
Spare length: (cutoff value λc) × 2
・ Vertical magnification: 2000 times ・ Lateral magnification: 10 times

1-4. Color tone of edge area | region The backlight of an Example and a comparative example was lighted, and the color tone of the edge area | region of backlight was visually evaluated from the front direction. One point that does not care about bluish at all, two points that do not have any problem in bluish but there are no problems in practical use, and three points that have strong bluish and a practically problematic level are considered as three points Based on the criteria, 20 subjects evaluated and calculated the average score. Those with an average score of 1.25 or less are “AAA”, those with an average score of more than 1.25 and less than 1.50 are “AA”, and those with an average score of more than 1.50 and less than 1.75 “A”, those with an average score of more than 1.75 and 2.00 or less are “B”, those with an average score of more than 2.00 and 2.25 or less are “B ⁻ ”, and the average score is 2 . A score exceeding 25 points was designated as “C”.

1-5. Angular Dependence of Color Tone The backlights of Examples and Comparative Examples were turned on, and the color tone near the center of the backlight was visually evaluated from various directions. One point where the change in color due to the angle is not worrisome at all, one point where the change in color due to the angle is slightly worrisome, but two points at a level that is not a problem for practical use, and the color change due to the angle is large and practical. Twenty subjects evaluated using the evaluation criteria which made 3 points the thing which is a problem level, and calculated the average point. Those with an average score of 1.25 or less are “AAA”, those with an average score of more than 1.25 and less than 1.50 are “AA”, and those with an average score of more than 1.50 and less than 1.75 “A”, those with an average score of more than 1.75 and 2.00 or less are “B”, those with an average score of more than 2.00 and 2.25 or less are “B ⁻ ”, and the average score is 2 . A score exceeding 25 points was designated as “C”.

1-6. Interference unevenness Under the fluorescent lamp illumination, the presence or absence of the interference unevenness of the quantum dot sheet of the example and the comparative example was visually observed. Those in which no interference unevenness was observed were designated as “A”, those in which interference unevenness was slightly observed were referred to as “B”, and those in which interference unevenness were strongly observed were designated as “C”.

2. Fabrication of Quantum Dot Refer to the method described in the technical document “Journal of American Chemical Society. 2007, 129, 15432-15433”, and the InP / ZnS core-shell quantum dot (quantum dot A And InP / ZnS core-shell quantum dots (quantum dots B) having a peak wavelength of 528 nm.
Next, quantum dots A are added to a mixed solution of aminopolystyrene (manufactured by SMA, trade name: SMA EF80) and epoxy resin (manufactured by Loctite, trade name: E-30CL) in a solvent. A polystyrene mixture was prepared. After the solvent of the liquid mixture is evaporated and the mixture is further cured to obtain a cured product, the cured product is pulverized with a ball mill, and quantum dots C formed by coating quantum dots A with aminopolystyrene and epoxy resin are obtained. Obtained. The same operation was performed on the quantum dots B to obtain quantum dots D in which the quantum dots B were coated with amino polystyrene and epoxy resin.

3. Preparation of quantum dot sheet [Example 1]
A barrier layer of 20 nm in thickness made of silicon oxide was formed by PVD on one side of a 12 μm thick biaxially stretched PET film to obtain a barrier film. Next, a light diffusion layer coating solution a1 of the following formulation is applied on one surface of a 50 μm thick biaxially stretched PET film so as to have a thickness after drying of 11 μm, and then it is irradiated with ultraviolet light to form a light diffusion layer To obtain a light diffusion film. Next, a light diffusion film, a barrier film, and a biaxially stretched PET film having a thickness of 50 μm were laminated in the order described above via an adhesive layer having a thickness of 3 μm to obtain a laminate A (see FIG. 3). The barrier film and the light diffusion film were pasted together so that the surfaces on the biaxially stretched PET film side of the both faced each other. Next, a laminate B was obtained by the same operation as described above.
Subsequently, the coating liquid b1 of the quantum dot containing layer of the following prescription is apply | coated and dried so that the thickness after drying may become 100 micrometers on the surface at the side of the biaxially stretched PET film of the laminated body A, and the quantum dot containing non-ionizing radiation irradiation A layer was formed.
Subsequently, the quantum dot-containing layer not irradiated with ionizing radiation and the surface on the biaxially stretched PET film side of the laminate B are made to face each other and laminated, and ultraviolet light is irradiated from the light diffusion layer side of the laminate A Curing of the curable resin composition was advanced to obtain the quantum dot sheet of Example 1.

<Light diffusion layer coating solution a1>
・ Pentaerythritol triacrylate 30 parts (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
-70 parts of urethane acrylate (manufactured by Japan Synthetic Chemical Industries, UV 1700 B)
・ 5 parts of photopolymerization initiator (manufactured by BASF, Irgacure 184)
・ Silicon-based leveling agent 0.1 part (Momentive Performance Materials, TSF4460)
・ 100 parts of urethane resin diffusion particles (average particle size 3μm)
・ 500 parts of dilution solvent

<Quantum dot containing layer coating liquid b1>
-100 parts of isononyl acrylate (monofunctional monomer, refractive index 1.45)
・ 5 parts of photopolymerization initiator (manufactured by BASF, Irgacure 184)
0.2 part of quantum dot A 0.2 part of quantum dot B 20 parts of internally scattered particles (spherical alumina, average particle diameter 1.5 μm, refractive index 1.76)
・ 5 parts of dilution solvent

Example 2
The quantum dots of Example 2 in the same manner as Example 1, except that the internal scattering particles of the quantum dot-containing layer coating solution b1 were changed to true spherical zirconia (average particle diameter 0.1 μm, refractive index 2.2). I got a sheet.

[Example 3]
Laminates A and B were obtained in the same manner as in Example 1 except that the light diffusion layer coating solution a1 was changed to the following light diffusion layer coating solution a2 and the thickness of the light diffusion layer was changed to 2 μm. Next, on the light diffusion layers of the laminate A1 and the laminate B1, the following overcoat layer coating liquid c1 is applied so that the thickness after drying is 120 nm, dried, and irradiated with ultraviolet rays to form an overcoat layer. A laminate A1 and a laminate B1 were obtained. Subsequently, the coating liquid b2 of the quantum dot content layer of the following prescription is applied to the surface on the biaxially stretched PET film side of the laminate A1 so that the thickness after drying becomes 100 μm, and the acrylic polyol and the isocyanate are completely removed. An unreacted quantum dot-containing layer was formed.
Next, the quantum dot-containing layer and the biaxially stretched PET film side surface of the laminate B1 are laminated to face each other, and aged at 50 ° C. for one week to advance the reaction between acrylic polyol and isocyanate. 3 quantum dot sheets were obtained.

<Light diffusion layer coating solution a2>
・ Pentaerythritol triacrylate 30 parts (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
-70 parts of urethane acrylate (manufactured by Japan Synthetic Chemical Industries, UV 1700 B)
・ 5 parts of photopolymerization initiator (manufactured by BASF, Irgacure 184)
・ Silicon-based leveling agent 0.1 part (Momentive Performance Materials, TSF4460)
・ 5 parts of urethane resin diffusion particles (average particle size 3μm)
・ 500 parts of dilution solvent

<Quantum dot containing layer coating liquid b2>
-Acrylic polyol 162 parts (manufactured by DIC, Acrydic A-807, solid content 50%)
-Isocyanate 32 parts (Mitsui Chemical Co., Ltd., Takenate D110N, solid content 60%)
・ Quantum dot C 0.4 part ・ Quantum dot D 0.4 part ・ Diluent 400 parts

<Overcoat layer coating solution c1>
・ 1 part of UV curable resin (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30)
-0.2 part of a photopolymerization initiator (manufactured by BASF, Irgacure 127)
・ Leveling agent 0.1 parts (manufactured by Dainichi Seika Kogyo Co., Ltd., Seika Beam 10-28 (MB))
-90 parts of dilution solvent

Example 4
The quantum of Example 4 is the same as Example 1 except that the internal scattering particles of the quantum dot-containing layer coating solution b1 are changed to true spherical styrene beads (average particle diameter: 3.0 μm, refractive index: 1.59). I got a dot sheet.

Comparative Example 1
A quantum dot sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the internal scattering particles were removed from the quantum dot-containing layer coating solution 1a.

Comparative Example 2
Comparative Example 2 in the same manner as Example 1, except that the addition amount of the urethane resin-based diffusion particles of the light diffusion layer coating liquid a1 was changed to 80 parts and the internal scattering particles were removed from the quantum dot containing layer coating liquid 1a. The quantum dot sheet was obtained.

Comparative Example 3
The quantum dot sheet of Comparative Example 3 in the same manner as Example 1, except that the addition amount of the urethane resin-based diffusion particles of the light diffusion layer coating liquid a1 was changed to 5 parts, and the thickness of the light diffusion layer was changed to 3 μm. Got.

Comparative Example 4
A quantum dot sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except that the addition amount of the urethane resin diffusion particles in the light diffusion layer coating liquid a1 was changed to 0 part.

4. Production of Backlight and Liquid Crystal Display Device A commercially available liquid crystal display device (7 inches diagonal) using a blue LED as a light source was disassembled, and the backlight was taken out. The backlight was an edge light type, and had a reflecting plate below the light guide plate, a light diffusion film and two prism sheets above the light guide plate. In the two prism sheets, the stripe lines were orthogonal to each other between the lower side and the upper side.
The light diffusion film is removed from the above-described backlight, and the quantum dot-containing sheets of Examples 1 to 4 and Comparative Examples 1 to 4 are disposed between the light guide plate and the prism sheet, and Examples 1 to 4 and Comparative Example 1 I got a backlight of ~ 4.
Next, the backlights of Examples 1 to 4 and Comparative Examples 1 to 4 are returned to the parts where the backlights of the disassembled liquid crystal display were installed, and the liquid crystal displays of Examples 1 to 4 and Comparative Examples 1 to 4 I got

  As is clear from the results in Table 1, the quantum dot sheets, backlights and liquid crystal display devices of Examples 1 to 4 have edge regions compared to the quantum dot sheets, backlights and liquid crystal display devices of Comparative Examples 1 to 4. It has been confirmed that the color tone and the angular dependence of the color tone can be improved.

10: Quantum dot containing layers 21a, 21b, 31a, 31b, 41a, 41b: light transmitting substrates 30a, 30b: barrier films 32a, 32b: barrier layers 40a, 40b: light diffusing films 42a, 42b: light diffusing layer 51a , 51b, 52a, 52b: adhesive layer 61: laminate A
62: Laminate B
100: quantum dot sheet 110: light source 120: optical plate 130: reflector 140: prism sheet 200: backlight 210: liquid crystal panel 220: holder 300: liquid crystal display device

Claims (11)

It is a quantum dot sheet, The quantum dot sheet has a quantum dot content layer containing a quantum dot and a binder resin which absorb primary light and emit secondary light, and any one surface of the quantum dot sheet The following condition A is obtained by vertically irradiating visible light with a halogen lamp (12 V, 48 W) as the light source and measuring the intensity of transmitted light in the range of -85 degrees to +85 degrees. -1 and a quantum dot sheet which satisfy | fills at least any one of conditions B-1.
<Condition A-1>
The sum of the intensity of the maximum value of the intensity of the transmitted light of -85 degrees to + 85 degrees to 1 and normalized -30 degrees to + 30 degrees when upon the _{P 30, P 30} is more than 50.
<Condition B-1>
The absolute value of α is equal to or greater than 30 degrees, where α is a diffusion angle showing an intensity half of the maximum value. The quantum dot sheet according to claim 1, further satisfying the following condition A-2.
<Condition A-2>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -45 degrees to + 45 degrees when upon the _{P 45, P 45} is more than 60. Furthermore, the quantum dot sheet of Claim 1 or 2 which satisfy | fills the following condition A-3.
<Condition A-3>
The sum of the intensity of the maximum value of the intensity of -85 degrees to + 85 degrees of the transmitted light to the 1 and normalized -60 degrees to + 60 degrees when upon the _{P 60, P 60} is more than 75. The quantum dot sheet according to any one of claims 1 to 3, further satisfying the following condition B-2.
<Condition B-2>
The absolute value of β is 45 degrees or more, where β is a diffusion angle showing an intensity of 1/3 of the maximum value.   The quantum dot sheet according to claim 1, wherein the quantum dot-containing layer contains internal diffusion particles. The refractive index _{n A} of the binder resin, when the refractive index of the inner diffusion particles was _{n B,} n B / _{n A} is the quantum of claim 5 is 1.02 or more, or 0.98 or less Dot sheet.   The quantum dot sheet according to any one of claims 1 to 6, wherein both surfaces of the quantum dot-containing layer are sandwiched between light-transmitting substrates.   The quantum dot sheet according to any one of claims 1 to 7, further comprising a light diffusion layer.   The at least one surface of the said quantum dot sheet | seat is 0.1-10 micrometers in arithmetic average roughness Ra of the cutoff value 0.8 mm based on JISB0601: 2001 in any one of Claims 1-8. Quantum dot sheet.   At least one light source emitting primary light, an optical plate disposed adjacent to the light source, for guiding or diffusing light, and a quantum dot sheet disposed on the light emitting side of the optical plate A backlight, wherein the quantum dot sheet is the quantum dot sheet according to any one of claims 1 to 9.   A liquid crystal display device comprising a backlight and a liquid crystal panel, wherein the backlight is the backlight according to claim 10.